Category Archives: Birding

Corvid of the month: Rooks

In honor of last week’s #CrowOrNo photo, I wanted to spend some more time spotlighting a corvid perhaps less well known to my fellow North Americans, the rook (Corvus frugilegus).

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Photo c/o Pam P.

Among corvids, adult rooks might be one of the most unmistakable species. Their naked, chalk colored chin, lores, and bill base gives their face an appearance resembling no other bird.  The grey crow, or bare-faced crow (Corvus tristis), shares a similar facial pattern but is easily distinguished by its rather blushing appearance and blue eyes.  In addition, whereas the grey crow is known mainly to the peoples of Papua New Guinea, rooks have one of the widest distributions of any corvid species, breeding from Sweden all the way to China.

(Hover over tiled photos for captions)

Of course, what made last week’s #CrowOrNo submission such a challenge was that the photo was not of an adult, but rather a first year bird.  With their nasal hairs intact, first-year rooks look something like a crow/raven hybrid. Although bill shape is, I think, the best tell, one other field marker to look for are their notoriously shaggy “pants” (belly and leg feathers) in contrast to crows and ravens.

The transition to bare-faced adult occurs during the bird’s first complete body molt when they’re around 10-15 months old.  This process can take as little as 25 days but for most birds occurs over the course of several months1.  The evolutionary reason for this loss may have something to do with their foraging habits, which consists largely of probing for worms, though this remains unclear.

Unlike many Corvus species which are more general with respect to their diet, rooks are fairly specialized to feed on the small worms that live among the roots of plants.  One consequence of this diet is that there are distinct boom and bust seasons.  In April and November, wet conditions make worms plentiful, but in other times of years drier conditions drive worms deeper and out of reach.  Since access to food can be precarious, rooks have adopted a rather unusual incubation strategy compared to most birds.  Rather that commencing incubation when the entire clutch is laid, which promotes the same hatch date, rooks start incubating the first egg as soon as it is laid.  This chick is born earliest, giving it a clear advantage over its future siblings.  If food becomes sparse only this chick will survive. If food remains abundant, the parents can provision enough to supply the larger, more dominant chick, and its younger siblings.2

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Photo c/o Danny Chapman

Rooks are distinct from other corvids with respect to their behavior as well.  In contrast to crows or ravens, rooks are essentially non-territorial.  During the non-breeding season they are most commonly found in large foraging groups (much to the chagrin of local agricultural farmers, I imagine).  During the breeding season they nest in colonies, rather than individual territories, though they will defend the area around their nest and their mate as necessary.  A nest is often reused by the same pair year after year until it is razed by weather, or the pair is forced for some other reason to construct a new nest.  Like many other Corvus species, they maintain a socially monogamous life-long mate.3

Cognitively, rooks demonstrate many of the same skills that have brought some of their peers into the global spotlight. For example, when in the care of humans, rooks have demonstrated an astounding alacrity for tool use, though they are not known for manufacturing tools in the wild. For example, captive rooks have been shown to bend wire into hooks to extract food out of a tube like New Caledonian crows, or work together to solve problems like chimps (though unlike chimps, they do not appear to understand when cooperation is necessary or how it works).4,5

Taken together, these snippets of their biology and behavior demonstrate what unique members rooks are to the Corvus genus.  I envy my counterparts across the Atlantic and Pacific and encourage them to take a second look at the rook whenever opportunities present themselves.

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Photo c/o Paul Wilson

Literature cited

1.  Dunnet GM, Fordham RA, Patterson IJ. (1969).  Ecological studies of the rook (Corvus frugilegus) in North-East Scotland.  Proportion and distribution of young in the population.  British Ecological Society 6: 459-473

2.Green P. (1996). The communal crow.  BBC Wildlife 14: 30-34

3. Coombs CJF. (1960). Observations of the rook Corvus frugilegus in southwest Cornwall Ibis 102: 394-419

4. Bird CD, and Emery NJ. (2009).  Insightful problem solving and creative tool modification by captive nontool-using rooks.  PNAS 106: 10370-10375

5.  Bugnyar T. (2008).  Rooks team up to solve a problem.  Current Biology 18: R530–R532

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Filed under Birding, Corvid diversity, Corvid of the month, Diversity, Uncategorized

Are you playing #CrowOrNo yet?

Crows, ravens, magpies, even blackbirds or other non-corvid species can be tricky to distinguish from one another if you’re a beginning or even experienced birder given the right angle or blurry photo.  While some of it is a matter of learning key field markers, a big part of effectively learning to distinguish these species is an eye for the subtle differences in portion or appearance that comes with practice.  I believe learning these skills is not only fun, but makes us more informed corvid lovers and birders.

To that aim, I’ve started a weekly #CrowOrNo “quiz” on my Instagram (@corvidresearch) and Twitter (@corvidresearch) accounts.  Every Wednesday at 11:30 AM PST, I’ll post one photo and it’s up to you to decide whether or not it’s really a crow.  At the end of the day I’ll share the answer and any tips or tricks that would have helped to discern the true species.  Play, share, or simply spectate.  Whatever you’re comfortable with is fine for me, as long as you’re enjoying the process and learning more about these wonderful animals!  Check out the photos below for examples from past weeks.  I hope to see you there!

Oh, and have photos you think would make good fodder for the game?  Send them my way!

Update: The game is also now available on the Corvid Research facebook page!

 

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Filed under Birding, Corvid trivia, Just for fun

New research on the cause of the AKD outbreak

Since the nineties, Avian Keratin Disorder has been an increasingly common disorder among Alaskan and PNW crows, chickadees (~17% of northwest crows1, ~6% of black-capped chickadees2) and a handful of other species, that causes gross deformities of the beak such as elongation, curvature or crossing.  I’ve written previously about the details of this disease before, but at that time there was little progress in determining the underlying source of the outbreak.  While AKD can be caused by a variety of things, at the scale it’s being observed now scientists questioned if there was a more consistent underlying factor.  Since AKD can cause discomfort or even death (primarily through the inability to feed or preen) understanding what might be the source of this outbreak has clear management and conservation implications.

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An AKD-afflicted American crow in Seattle, WA.

Among the initial suspects were environmental contaminants such as heavy metals, organic pesticides, and toxic environmental pollutants like PCBs, PCDDs, and PCDFs.   Blood work done on afflicted Northwestern crows, however, showed no significant difference in the 30 blood elements tested compared to unaffected adults or juveniles3.  Fortunately, new research may finally be shedding light on what’s going on.

Disease can be an easy thing to rule out if you know what you’re looking for, but new to science pathogens can evade traditional diagnostic techniques.  To account for this, a team of USGS and university scientists conducted a sequencing study comparing pooled RNA of healthy and AKD positive chickadees, crows and nuthatches in attempt to identify a candidate pathogen2.  Their work appears to have paid off, revealing evidence for a new picornavirus (a family of viruses previously known to science) they are calling poecivirus.  Whereas 100% of AKD-affected birds (23 subjects) tested positive only 22% of the 9 control individuals did.

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Alaskan black-capped chickadee with severe AKD. Photo c/o Martin Renner

Given these small sample sizes, it’s too early to throw our hands up in complete relief of having identified the cause of the AKD outbreak, especially since there’s still much to be done in understanding the potential relationship of this new virus to the environment.  Nevertheless, these findings offer some insight and hope that scientists are on the right track.  With more dedicated work we may soon have a much better understanding of this novel pathogen, its link to AKD, and management options moving forward.

Literature cited

1.  Van Hemert C, & Handel CM. 2010.  Beak deformities in Northwestern crows: Evidence of a multispecies epizootic.  The Auk 127: 746-751.  doi: http://dx.doi.org/10.1525/auk.2010.10132

2. Zylberberg M, Van Hemert C, Dumbacher JP, Handel CM, Tihan T, and DeRisi JL. 2016. Novel picornhttps://wordpress.com/post/corvidresearch.wordpress.com/3363avirus associated with Avian Keratin Disorder in Alaskan birds.  mBio 7 doi: 10.7589/2015-10-287

3. Van Hemert C, Handel C. 2016.  Elements in whole blood of Northwestern crows (Corvus caurinus) in Alaska USA: No evidence for an association with beak deformities.   Journal of Wildlife Diseases 52:713-718 doi: http://dx.doi.org/10.7589/2015-10-287

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Filed under Birding, Corvid health, Crow curiosities, Crow disease, Crow life history, Ecosystem, Uncategorized

15 of the prettiest corvids from around the world

When most Americans think of corvids, the color palette that probably comes to mind is black, grey, blue, white and iridescent.  Together, these colors have certainly assembled a handsome collection of birds, but there’s an awful lot more pigments in the corvid family than that.  Even among those colors, some of the more topical corvids exploit them in dazzling ways.  Unlike American or New Caledonian crows though, these birds have not gotten their fair share of the corvid limelight and it’s time we change that.  The following is a sample of just some of the corvid diversity more folks should know about.  If you really want to have a little extra fun, ignore the scientific names and see if there are any birds you would group together in the same genus (reminder: Family>Genus>Species).  Then you can go back and look at the first part of the scientific name to see if you were right!

These photos were primarily sourced from some of the generous and talented photographers that can be found on Flickr.  Please click on their names to see more of their great work.

1. Common green magpie (Cissa chinensis).  Found in parts of India, China and Indonesia.  A flocking corvid often found low in the canopy where they can be very difficult to spot among the vegetation.  According to the International  Union on the Conservation of Nature (IUCN) their populations are considers stable and of least concern.

2. Taiwan Magpie (Urocissa caerulea).  Endemic to Taiwan, these are flocking corvids that feed mostly from tree canopies.  Their populations are stable.

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Photo c/o Dave Irving

3. Lidth’s jay (Garrulus lidthi).  The only jay endemic to Japanese islands of Amami-oshima and Tokunoshima.  In the fall they can gather in groups as large as 100 birds where they feed mainly on acorns.  Habitat loss and predation have this bird listed as declining and vulnerable.

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Photo c/o Mark Curley

4. Unicolor jay (Aphelocoma unicolor).  Ranges intermittently from western Mexico to El Salvador and may have as many as 5 subspecies! They are considered of least concern, though populations are declining.

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Photo c/o Maynor Ovando

5. Green jay (Cyanocorax yncas). These jays can be found from southern Texas throughout central America and as far south as Peru.  Although they are a solitary breeder, they are very social in the non-breeding season.  Populations are increasing and they are considered of least concern.

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Photo c/o Wade Strickland

6. Spotted nutcracker (Nucifraga caryocatactes).  Native across Europe and Asia, theses birds are monogamous and generally hang out only with their mate.  Like the unicolor jay they are considered of least concern but trends point towards decline.

eurasian-nutcracker

Photo c/o Dave Irving 

7. Ceylon magpie (aka Sri Lanka blue magpie; Urocissa ornata).  Another Sri Lankan endemic.  These birds can be seen in pairs or small flocks where they noisy work the tree canopy.  They are considered vulnerable and declining.

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Photo c/o Dave Irving 

8. Black-throated magpie jay (Calocitta colliei).  This bird is limited to northwest Mexico where it can be found in open woodlands chatting loudly and waiving their tails.  They are common and populations are stable.

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Photo c/o Ahmed Eldaly

9. Turquoise jay (Cyanolyca turcosa).  Can be found in the humid forests of Ecuador, north Peru, and south Columbia.  Overall this species is poorly documented.  Right now it is considered a least concern species but it’s possible that’s due to lack of data.

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Photo c/o Dave Irving

10. Rufous treepie (Dendrocitta vagabunda).  Found across India and southeast Asia.  These birds are generally wary of people but have been known to enter houses to look for geckos.  Would love to find one in my house!  Populations are stable and they are considered least concern.

11.  Gold-billed magpie (Urocissa flavirostris).  Endemic to Taiwan, these birds keep their tails erect when on the ground, possibly to prevent the feathers from being damaged. Populations are stable and they are considered of least concern.

12. Bornean green magpie (Cissa jefferyi).  Found only in Indonesia and Malaysia, these birds look (and act) similarly to the common green magpie.  Relatively little is known about this species as they are hard to access high in the mountain forests.  It’s listed as of least concern.

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13. Eurasian jay (Garrulus glandarius) Found throughout Europe, Asia and Northern Africa.  This bird is common to most birders outside of North and South America.  Although these birds remain with their mates for extended periods they do not keep much contact throughout most of the year. Eurasian jays are in no danger of global population decline.

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Photo c/o Simon Forster

14. Azure-winged magpie (Cyanopica cyana).  Native across Asia and as far north as Mongolia and southern Siberia*. They form small family parties during the breeding season but amass into large groups during the nonbreeding season.  Populations are increasing and they are of least concern.

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Photo c/o Crotach

15. Finally we have, literally, the beautiful jay (Cyanolyca pulchra). Found only in the Andes of Colombia and north Ecuador.  They can be found alone or in pairs but are not believed to interact in large social groups.  Little known about reproduction, social behavior or predators.  Populations are declining and near threatened.

beautiful-jay

Photo c/o Andrew Spencer

Did you pick out a favorite bird?  Let me know in the comments and I’ll try to dedicate a post to it!

Literature cited

*A previous version of this post incorrectly stated that the Azure-winged magpie spread as far west as Spain and Portugal.  Although this was true at the time the reference guide used to write the post was written, since 2002 these western birds have been splint into their own species called the Iberian magpie1.

1Fok KW, Wade CM, Parkin DT (2002). “Inferring the phylogeny of disjunct populations of the azure-winged magpie Cyanopica cyanus from mitochondrial control region sequences.”. Proc. Roy. Soc. B Biol. Sci. 269 (1501): 1671–1678.doi:10.1098/rspb.2002.2057.

All other species descriptions were based on: Madge, S. and Burn, H. 1999.  Crows and jays.  Princeton, New Jersey: Princeton University Press 1999.

 

 

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Filed under Birding, Diversity

American crow nesting ecology 101

*This article was updated and renamed from Everything you want to know about crow nests on April 14th, 2020.

Spring marks one of my favorite times of year. Cherry blossoms abound, the rain smells sweet and the birds get busy putting their carpentry skills to good use. In fact for me, there’s nothing more iconically spring than watching the silhouettes of crows with bill loads of timber or soft material dot the skies as they shuttle back and forth to their nest trees. Like a townhouse development, these construction projects are over in the blink of an eye and soon, their bill loads of twigs will be replaced by food for their mate and, eventually, their insatiable young. Watching your local nest is both a great way to learn more about your neighborhood crow family, and avoid unpleasant conflicts with protective crow parents.  Whether you’re years into this tradition or just getting started, there’s always more to learn and enjoy!

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Nest site selection, construction, and reuse

Nest construction is initiated anytime from early February to late April, depending on the region.  In Washington, nest construction generally kicks of by the second week of March. Crows will nest in an astounding array of places, depending on where they live and what’s available.  In Seattle, I see them nest anywhere from the eaves of skyscrapers, to the crooks of well concealed tree limbs, to within reach in saplings that are struggling to support their weight. In areas where appropriate trees are unavailable they may even nest right on the ground!¹ How crows make their precise nest site selection is unknown, but most commonly in the PNW, nests are placed close to the trunk in a fork or on a horizontal branch in the top third of a conifer.

Both the male and female participate in building the nest. In areas where auxiliary helpers are present, helpers may also contribute to gathering nesting materials and may add these materials themselves, or leave for the female to work in.

If trees are abundant, the nest exterior is constructed mainly from twigs pulled from live trees.  In areas where such materials are in short supply, nests may be composed of as much as 50% grass and other plant stems.² After the bulk of construction is complete, they’ll line the cup of the nest with soft materials like grass, bark, moss, flowers, mud, cow dung, roots, paper, fabric, fur, etc. Fur may be found or collected from live animals, as this large-billed crow (Corvus macrorhynchos) demonstrated on a panda at the Beijing Zoo in 2015.  Contrary to the news anchor’s fears, this would not have been painful for the panda. 

It takes 1-2.5 weeks to finish a nest, though second attempts can take as little as 5 days in areas where helpers are present.  A new nest is usually about 1.5 ft across and 8-10 in deep. The life of a typical nest is only about 10 weeks (1-2.5 weeks of building, 6 days of laying, 20 days of incubating and 4 weeks of nestlings) though they are hardy structures and can remain intact for years. After the young fledge, the crows will not return to the nest. Generally speaking, crows will only use a nest once, though the occasional observation of a pair repairing and reusing an old nest have been reported across the country. More often it appears that if they are going to reuse a nest site, they will build on top of an old nest, particularly in areas where nest trees are especially sparse like downtown Seattle. This also appears to be more common in the Midwest.

Eggs and nestlings

Egg laying may begin immediately, or up to a week after the nest is complete.  Crows, like nearly all birds, have a single ovary and oviduct and can only lay one egg a day.  In some cases they may even skip a day or two between laying. Crows generally lay a clutch of 4-5 eggs, but nests with up to 9 eggs have been observed, though it’s possible this was the result of a second female laying in the same nest.³  Females will usually start incubating the nest once the third egg is laid. To aid with incubation, females develop a patch of featherless skin on their underside called a brood patch.  Brood patches are common in birds, and generally only occur on females but observations of male crows with brood patches have been reported. Only female crows incubate, though eggs may be briefly “incubated” by helpers.

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Common raven eggs left | American crow eggs right

For a couple of days before the full clutch is laid, the female will sit next to the nest and give begging calls.  This behavior continues even after she starts incubating, which in Seattle is most often the explanation for begging calls emanating from nests during April. Both her partner and helpers will bring her food, usually 2-4 times an hour. She may hop off the nest to help chase away threats, feed, preen, or stretch, but generally doesn’t leave for more than a few minutes.

The eggs will start hatching after about 15-20 days of incubation.  Since the female starts incubating before the full clutch is laid, crows exhibit asynchronous hatching, where not all the young hatch on the same day. In other species of birds like mallards, even though the eggs were laid days apart, the young all hatch within a few hours of each other because the female waited to start incubating until only after all the eggs were laid.

Like other songbirds, crow chicks are altricial and nidicolous, meaning they hatch blind and helpless, and will remain in the nest for many days after hatching.  Ducks, chickens, quails, etc. all produce precocial, nidifugous young which hatch sighted, covered in downy feathers, and ready to follow their parent(s) away from the nest within a few hours.

baby crow

Once the eggs start to hatch the female will continue to brood the nestlings continuously for the next couple of weeks.  Once the nestlings are more developed and covered in feathers, she will brood less and less often and transition mostly to food provisioning.  Nestlings appear to be fed primarily invertebrates, but their diets vary depending on local resources.  For the first couple of weeks after hatching, nestlings are fed about every 30min by parents and helpers, if they are present. After about 4 weeks the young will fledge (leave the nest permanently). Prior to fledging you may see the nestlings sitting on the rim of the nest and flapping around awkwardly.  Not all fledglings are flighted at the time of leaving the nest, so take care not to assume young have simply fallen out. After the chicks fledge, they remain in the care of their parents for the duration of summer, and will continue to be fed for about 4 months.

Differences among corvids

Crow, jay and raven nests are similar in shape and choice of materials and mostly differ in overall size. The main standout are magpies,  which build incredible domed-shaped nests the size of a large beach ball.  The nests require so much material that they can take as much as 40 days to build.  Japanese jungle crows are another species of note, as they have a (relatively) new and problematic habit of building nests out of wire hangers and causing massive blackouts.

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A Jungle crow nest in urban Japan. Photo: Götz

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The magpie’s nest is the big clump in the middle of the tree.

Avoiding conflicts

Most breeding related dive bombs occur as the result of a person being too close to a fledgling, but some crows get feisty around their nest too. Physical contact between birds and people during these altercations are rare, but can happen and might hurt. In areas where crows are less persecuted (like cities) they tend to be more aggressive than their rural counterparts. If you know where a nest is and can avoid it, do so and save everyone the aggravation. Otherwise a good strategy is to invest in an umbrella you don’t care about.  It’s a simple and inexpensive solution that protects both yourself and the legacy of recognizing that outdoor spaces are shared space between ourselves and wildlife.

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Crows build their worlds on our backs.  We might as well lean in and appreciate the joys of watching nesting birds!

Have more questions? Let me know in the comments!

 

  1. Gross, A. O. (1946b). “Eastern Crow.” In Life histories of North American jays, crows, and titmice., edited by A. C. Bent, 226-259. U.S. Natl. Mus. Bull. 191
  2. Good EE. (1952). The life history of the American Crow Corvus brachyrhynchos Brehm. Phd Thesis, Ohio State Univ., Columbus.
  3. Peck, G. K., and R. D. James (1987). Breeding Birds of Ontario: Nidiology and Distribution. Volume 2: Passerines. Miscellaneous Publications of the Royal Ontario Museum, Toronto, ON, Canada.

Most of the general information was sourced from:

  1. Verbeek, N. A. and C. Caffrey (2020). American Crow (Corvus brachyrhynchos), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi-org.offcampus.lib.washington.edu/10.2173/bow.amecro.01

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Filed under Birding, Breeding, Crow behavior, Crow life history, Crows and humans

Australian magpies are not corvids

Ah the Australian magpie.  With its glossy tuxedo plumage, heavy bill, and charismatic reputation it’s no wonder it’s a favorite among corvid lovers.  Why then, do scientists keep insisting that it’s not, in fact, a corvid?  This insistence of ours can feel arbitrary, even perhaps insulting, to a bird that superficially looks and acts like the corvids we know.

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A still frame from the infamously cute video of an Aussie magpie and a puppy play-wrestling together.  

To address this question, corvid expert and my colleague, Jennifer Campbell-Smith, recently penned a terrific piece to lay the confusion to rest.  I recommend everyone take the time to read it in full.

If you do not have time, the short version of the story is that physiologically, Australian magpies, like the other butcherbirds they are classified with, lack the nasal bristles indicative of corvids.  Genetically, DNA work done in the late 80’s also showed that, while they share a common ancestor, are are phylogentically  distinct from other corvids.  There has been some back and forth since then on the details, but there’s no scientific evidence that we should be lumping them in with corvids.

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The nasal feathers are those thin, wire like feathers covering the base of the bill on the crow to the right, but conspicuously absent on the Aussie magpie to the left.  Australian magpie photo: Guy Poisson

Why this bums so many corvids lovers out is a curious mystery to me.  Personally, I find the convergent evolution with respect to both appearance and behavior much more interesting than if we simply made a taxonomic mistake.  As for whether corvid lovers should continue to find joy and fascination in observing these birds well, I’ll direct you to this video and let you be the judge.

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Filed under Being a scientist, Birding, Crow curiosities, Crow life history, Taxonomy

Baby crow detective work

By now, most of us have come across these images of  “baby crows” so often it induces more of a yawn than a fit of aggravation.
Image-1If, somehow, these images are new to you feel free to check out my post fully debunking them, as I will not dedicate any further time to them here.   But there’s a new photo circulating social media, and it makes for a much more compelling crow doppelganger;

baby crow
You’ve got three, black, altricial baby birds in a nest and really, they’re not terribly un-crow like.   It doesn’t make you a complete crow rookie to make this mistake, but there are some key things wrong here.  And this is the moment where, as a scientist, these photos elevate from being simply another source of annoying misinformation (which, they are) to the kind detective work that childhood doctor visits fostered a deep love for.  Because, not unlike my favorite activity in the Highlights magazines I anxiously parsed through in those waiting rooms, there are 4 things that are different between these two photos and it’s up to you to find them.  So take a minute and see what jumps out at you….

Crows_v_no crows
Figured it out (or given up)?  The first thing to know is that all bird species are very specific in terms of both nest materials and nest construction.  Sure, some birds can happily use some ribbon in place of straw (like orioles) or build nests in old shoes just as easily as in gutters (like bewick’s wrens) but the basic style is always the same.  Robins will always use mud as a binder and bushtit nests will always look like cozy sleeping bags made of moss.  Knowing that, the material used in the nest on the right should jump out as a red flag.  Of course you’ll find crow nests with a bit of string, fabric or grass (especially for lining) but the bulk of the nest is always made of pinky-wide sticks.   Really, you need look no further at this point to know immediately that the photo on the right is an impostor but let’s keep going because it’s fun.

Next let’s look at the babies themselves, which is where the three remaining differences are.  Two of them are color-coded, did you catch them?  Ah yes, gape and eye color.  See that brightly colored area on the corner of the bird’s developing beak?  That’s called the gape, and the bright color that flashes when they open their mouths is a powerful signal that tells parents to “insert food here”.  Crows have bright pink gapes, whereas these other birds have yellow gapes.  Our other color coded giveaway is the eyes.  Granted the lighting is not great, but it’s clear that the crows on the left have light blue eyes whereas these other birds have dark eyes.  In some species of crow the babies are born with brown eyes that turn blue as they age, but such is not the case with our American crows and you can expect that nestlings will always have blue eyes.  The last clue, which takes more expert level knowledge to notice, is the bill shape.  The birds on the right have a slightly more embellished curve to the bill than a typical crow chick.

The final mystery, of course, is what the birds on the right actually are.  Unfortunately, I failed to track down the original poster, but as best I can tell they’re black drongo chicks.  Black drongos are members of the drongo family (Dicruridae) and are native to Southern and Eastern Asia.  Here’s another photo I found that looks consistent with the previous one.  If any drongo experts read this blog though and want to correct me, I’d love to hear from you!

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Filed under Birding, Crow life history

Yellowstone field experience

Last week I had the great pleasure of spending a week in Yellowstone National Park with both corvid expert, John Marzluff and predator-prey dynamic expert, Aaron Wirsing.  In addition to spending an entire week with these two, I also had meetings and saw presentations from folks like the golden eagle team of Al Harmata and Marco Restani, the head researcher of the wolf project, Doug Smith, Bison expert Rick Wallen, and wolf and cougar kill expert Dan Stahler.  It was an amazing week of breath taking wildlife and in depth expertise on what’s going on in the park.  This week, I thought it would fun to take a little break from corvids and just share some of the photos I took along with the stories and biological details that go with them.

Birds
Ungulates
Predators
Miscellaneous

Birds

To kick the trip off we headed outside of Bozeman, Montana to meet up with eagle researchers Dr. Al Harmata and Dr. Marco Restani.  They’ve been doing research on eagles for more than 30 years and know more about these birds than maybe anybody.  Right now, they’re conducting an ongoing study to look at the effects of lead poisoning on  eagles.  Although lead shots have been banned in waterfowl hunting and in some states like California, in most other places lead bullets are still used for other kinds of game.  The lead fragments end up in the gut piles hunters leave behind, or in the prairie dogs or other carnivores that their shooters had no intention of taking home.  Eagles scavenge these remains and can wind up with deadly levels of lead in their bloodstreams.  Elimination of lead from bullets will likely be a necessary step to protect eagles, though I expect a robust fight from the NRA and some hunting communities.

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For corvids, spring time means nesting time and the magpies were busy at work.  Unlike crows and ravens which build more traditional looking nests, magpies make nests with roofs, further protecting them from predators.  If that’s not cool enough, magpies are known to build several of these dome nests and have been observed moving both eggs and chicks between them.

The magpie's nest is the big clump in the middle of the tree

The magpie’s nest is the big clump in the middle of the tree

A bill-load of mud to finish off lining the nest

A bill-load of mud to finish off lining the nest

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Seeing peregrine falcons perched along the 520 bridge on my way to school is always a treat, but there’s something about seeing them in this setting that’s all the more spectacular.

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At lunch time we were greeted by John’s special raven friend, Big Guy, which has been visiting him in the park for the last 15 years.  He and his mate were also busy nest building though we were unable to locate it.

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Mountain bluebirds were such a spectacular addition of color to the park, and I was super lucky to be in the right place at the right time to snap this photo.

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Ungulates

When we first arrived to the park, we were surprised to be greeted by pronghorn.  John has been leading classes to Yellowstone for 15 years and had never seen them as far into the park as we did.  Pronghorn aren’t adapted to run very well in deep snow, so they generally avoid the higher elevations in the park until later in the year. The snow melt came incredibly early this year, however, allowing them to penetrate further into the interior of the park than usual.  While the level of early snow melt we experienced isn’t unheard of, it was unusual and fit the models that predict increased drought in this area as a result of climate change.

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Bighorn sheep were prolific across the park.  In the winter and spring, male bighorns form large groups while the ewes and lambs heard up to do their own thing. I never got tired of seeing those big curls!

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Bison are truly the iconic ungulate in the park.  Theirs is a story of an amazing comeback, and one that’s really not so different from wolves.  As of 1902 there remained only 23 bison left in the park, and but thanks to ranchers and the US Army administrators of YNP, new animals were brought in and over the next 50 years that small population grew to over a 1000 animals.  Now, the park supports about 4000 animals, and is considered the only place in the country that has both maintained bison since prehistoric times, and supports non-cattle hybridized bison.

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Right now, bison regulation within the park is subject to much debate due to the presence of brucellosis.  Brucellosis is a bacterial infection that was brought when settlers first introduced cattle to the west.  It results in the abortion of calves in animals like bison, elk and livestock.  It’s transmitted by contact with an infected mucous membrane, which generally happens when curious animals touch and smell the aborted calves.  Although it’s not fatal to the mothers, the aborting of calves represents a potential economic threat to ranchers.  Although elk are also important vectors of this disease, a rancher we spoke with echoed the opinion of the ranching community at large in saying that bison are the main problems and their departure from the park needs to be controlled.  As of 2002, the Sate and Federal government developed an inter-agency management plan to control bison and the spread of the disease, which basically means that many (think in the thousands) of animals are killed once they cross the boarder.  Lead park bison biologist Rick Wallen described to us the controversial nature of this tactic which results in, one the one hand, folks from the ranching community saying there isn’t enough being done, while on the other, members of the public decrying the park for killing such an iconic species.  Despite these culls, however, the park maintains a stable population of bison, which other than run-ins with lakes and geothermal features, are basically free from predation apart from one particular wolf pack which occasionally manages to take one down.

One of my colleagues illustrating the difference between cow (left) and bull (right) bison horns.  She also sports a radio transmitter used to track an individual bison across the park.

One of my colleagues illustrating the difference between cow (left) and bull (right) bison horns. She also sports a radio transmitter used to track an individual bison across the park.

A couple of bison playfully testing each other

A couple of bison playfully testing each other

One of the most interesting insights from Rick was the observation that bison both engage in what looks like altruistic behavior, like the time he witnessed a heard protect an injured female from wolves, to completely brutal behavior like the scene my classmates and I had the serendipitous opportunity to witness.

We happened upon this scene when checking the area for signs of a bear we had heard was scavenging some bison carcasses. Although we didn’t see the bear, we quickly noticed that there was a bison calf trapped in the water, and not too far from drowning by the sounds of its breathing. The banks of these lakes are incredibly slick, and it can be impossible for an animal to get out. We watched with bated breath, conflicted between rooting for the bison to make its escape and for it to drown, as that would mean an almost guaranteed bear and wolf sightings the following days. Finally after about 10 minutes the calf managed to pull itself from the water. While all this was going on, its heard had been nearby and quickly after the calf escaped began to approach it. We were all expecting a Disney style reunion but to our shock the entire heard proceeded to haze the calf! They pushed it about 100 m down the valley before finally relaxing their assault and letting the calf rest and start to graze. Since we didn’t see bears the next day, our best guess is the calf managed to regain its strength and make it through the night.

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A tree shows some ears after being used as a scratching post for a bison.

A tree shows some wear after being used as a scratching post for a bison.

Although much of our time in the park was dedicated to simply looking for, and observing wildlife, we also collected a couple of different kinds of data while we were there.  For the last 7 years this class has been conducting “elk follows” which means that we select an individual elk in the different parts of the park and record its activities for 15 min.  Later, we will use this data and match it up with data from the Wolf Project to ask questions about elk behavior, condition, and spatial use in light of the presence of wolves.  This big bull was taking a little rest and is a great illustration of the hardship of winter.  You can clearly see the low fat reserves on its rump, as evidenced by the outline of its spine and pelvic bones.

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This bull is a good example of one that’s already lost its antlers, and it’s probably feeling a little lighter than its 5-point companion, since elk antlers can weigh up to 40lbs!  Antlers are the fastest growing tissue and in the height of spring and early summer they can grow up to an inch a day.  One of our faculty members, Aaron Wiring, told us an incredible story of seeing a big 6 point bull being chased by wolves in an earlier trip, only to loose one antler during the chase. A little lopsided, the bull managed to fend them off until it was finally cornered against a tree when, you guessed it, the second antler fell off.  It was all over soon after that. Talk about bad timing!

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Predators

A coyote makes off with the leftovers of a bison carcass.  Coyotes are often killed by wolves, and they need to be extra mindful when in open spaces near kills sites like this.  Why wolves are so predatory towards coyotes and not foxes is something of a mystery.

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One of my favorite experiences while in the park was seeing the wolves.  There’s just something about seeing such an iconic animal that lifts your spirit.  The reintroduction of wolves was, and still is, incredibly controversial.  There’s no doubt that their presence on the landscape is a threat to ranchers and pet owners alike, but I was inspired by our talk with Hannibal, a rancher who lives adjacent to the park boundary.  Despite loosing three dogs and many sheep and calves to wolves, he maintains his position that they are a necessary part of the Western landscape and deserve a place along side he and his family.  After his daughter, Hilary Zaranek, started range riding (rounding up and sleeping with the heard at night) predation by wolves dropped to nearly zero and their three current dogs seemed very happy to me.  By shifting the ranching paradigm to one where multiple ranchers join herds and share space, range riders become a sustainable and economical option for ranchers.  Hannibal and Hilary are the forefront of this shift and their dedication to the presence of wolves was awe inspiring.

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While we were in the park we were privy to some pretty special changes going on within the packs. Inside the park, wolves are killed almost exclusively by other wolves.   Recently, the alpha male of the Lamar Valley pack was killed by members of the competing Prospect pack after he confronted them.  His death put the alpha female in an incredibly precarious position since she will be unable to hunt after she gives birth to her dead mate’s pups and in a few weeks.  Although her 6 current pups are nearly a year old they are still too young to provide for her during this time.  As a result, she is attempting to court 4 of the male members of the Prospect pack in an effort to gain a new alpha male that will help raise her pups.  Unlike lions which will kill the cubs of a competing male, wolves will help raise the former dad’s pups after they take over.  Some readers may even be familiar with the famous story of 8, the hero ‘little wolf” who did just this.  While we were in the park the female appeared to be courting a spectacular grey male, but shorty before we left we learned that he fell out of contention.  Who the next alpha male is is up to the alpha female, and only time will tell who she chooses.

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The effects of wolves in the park have been profound and their necessity to maintain a balanced and healthy ecosystem is unquestionable.  For more information on the wolves’ effects on the Yellowstone ecosystem check out this Ted talk.

One of the most interesting things we did was meet up with wolf expert Dr. Dan Stahler.  He and fellow carcass expert, Kai, lead us to a recent cougar kill and described how to identify kills as either wolf or cougar and showed us the kinds of data they collect off such kills.  Key signs off cougar kills are puncture marks around the throat, neat, cleanly picked bones, and characteristic caching (or covering and hiding) of the carcass.  Wolf kills, on the other hand, are not hidden, show signs of hemorrhaging around the animal’s back legs, and the carcasses are found dismembered.  This particular cow elk was killed and partially eaten by a cougar before being discovered by wolves and other scavengers.

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Miscellaneous

A badger skull found while hiking the bighorn lambing grounds on the edge of the park boundary.

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On our last day I spotted a couple of yellow-bellied marmots, marking the fist time John has seen them inside the park during this trip.  I’ve never gotten such a good look at these little animals and I must say they’re very pretty!

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Antler drops are an important source of calcium for many animals in the park, and this particular one shows its age with a beautiful patina of lichen.

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A bison carcass lays peacefully in its resting place of Lamar Valley.

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Filed under Being a scientist, Birding, Field work

Do crows reduce other songbirds?

Updated with data from a new review of studies looking at impacts of corvid removal on other birds.

A comment I occasionally hear, especially while conducting my research in neighborhoods is, “Ugh, I hate the crows.  All of a sudden we have tons of crows and they’ve scared off all our songbirds!”  This comment always pains me, but I understand that for most people it arises from a genuine concern for songbird abundance and conservation.  First off, as a reminder crows are songbirds themselves; ravens are our biggest songbird.  Semantics aside, I understand that there are many, many bird lovers who just can’t get on the crow bandwagon and when they talk about wanting songbirds at their feeders they mean chickadees, juncos, grosbeaks, etc.  They feel that since the “arrival” of the crows their observations of these other birds have diminished.  So is there anything to this?  Do crows indeed drive down populations of small, “desirable” backyard birds?

I came across this grizzly scene while conducting research in Bellevue.  An adult robin calling frantically while a crow munched on one of its young.  Later that same week I would watch of pair of adult crows chase hopelessly after a cooper's hawk that had taken one of their offspring.   I came across this grizzly scene while conducting research in…

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Filed under Birding, Crow behavior, crow conflicts, Crow life history

Crows: A birdwatcher’s best friend

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A Wompoo Fruit Dove

In every habitat in every country there’s always a particular species you can count on to give away interesting and cryptic critters.  When I was conducting research in the eucalyptus forests of eastern Australia it was bell birds, a small green bird with a distinctive bell like call that echos through the forest at a numbing consistency all day long.  While their conspicuous and raucous nature made them tempting to ignore, these birds were often the first on the scene when interesting new species entered the forest, and by learning their alarm calls I discovered far more birds, especially predatory birds, than I would have on my own.  A favorite moment was being the only field tech on my crew to glimpse a wompoo fruit dove, a particularly beautiful and secretive dove native to this area.  Given its beauty spotting this bird was high on all our lists, but it wasn’t until the end of the field season when my attention was caught by some rather rowdy bell birds that I actually got to see one.  Had I grown completely accustomed to ignoring the ringing calls of the Bell Birds, I might have missed what was one of the birding highlights of my time in Australia.

Here in the states, crows are often our bell bird equivalent.  While crows get a bad wrap from birders for depredating and depleting backyard bird populations this is unfounded.  In fact, I think crows make an excellent companion for a birder if you know what to look for.  Cryptic hawks or owls that you would never know are sitting quietly in the trees above you are given away by the loud aggressive alarm calls of crows.

While nest searching in Mercer Island’s Island Crest Park this morning I couldn’t help but be drawn to the scolds of about a dozen crows across a ridge in the ravine of the park.   The quick staccato and harsh tone of the call is easy to recognize with some practice, especially when it’s being given by several birds at once.

The Barred Owl often found hanging around our office on campus

The Barred Owl often found hanging around our office on campus

Peering across the ridge I couldn’t make out much through the branches, but sure enough after a few minutes of waiting came the unmistakeable “who cooks for you” call of a barred owl.  Another one quickly responded sending the crows into a fervor, and after a couple more dive bombs the owl emerged from its mossy post and opted for a quieter resting place away from the crows.  My feelings about the detriment of Barred Owls aside, there’s something unmistakeably thrilling about seeing an owl for a birder, and probably for most people.  They’re cryptic and undeniably charismatic, a good combo for making an exciting bird and, as has been the case for many birds before it, I wouldn’t have spotted this one without a little help from the crows.

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Filed under Birding, Crow behavior