Spring marks one of my favorite times of year. Cherry blossoms abound, the rain smell sweet and the birds get busy putting their carpentry skills to good use. Starting early March, the silhouettes of crows with bill loads of timber or wads of soft material dot the skies as they shuttle back and forth to their nest tree. 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. Spotting these nests is both a great way to observe and engage with your local crow family and avoid unpleasant conflicts with protective crow parents. With a little knowledge and a bit of practice, tracking down your resident crow nest will become one of your favorite spring traditions in no time.
Nest construction and site selection
Nest construction begins in early March and will continue (as nests fail) through about June. It takes 1-2 weeks to finish a nest after which the female will lay a clutch of 2-6 eggs. Unlike similarly sized squirrel nests (aka: dreys) which are made of leaves, crow nests are made mostly of pencil-width twigs. A new nest is usually about 1.5 ft across and 8-10 in deep. After the bulk of construction is complete, they’ll line the cup of the nest with soft materials like grass, tree bark, moss, flowers, paper or fur. Once we saw a crow ripping out the hair of an outdoor mannequin, no doubt to use as lining material.
Crows will nest in an astounding array of places, from the eaves of skyscrapers to the crooks of well concealed tree limbs. They can tower in the sky or be almost within reach. Most commonly, I see them built close to the trunk in the top third of Doug fir trees, but this is, of course, specific to the PNW. Both partners participate in nest construction. Helpers will aid to some degree but most of the work is left to the parents.
Differences among corvids
Crow, jay and raven nests are similar in shape and material but differ in overall size in accordance with the size of the bird. The main standout are magpies, which build incredible domed-shaped nests the size of a large beach ball. The nests require so much material, 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.
The life of a typical nest is only about 9 weeks (1-2 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 in a tree for years. After the young fledge, the crows will not return to the nest. Crows will only use a nest once, and generally only fledge one brood a year. They will, however, 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.
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. Crows in areas where they are less persecuted (like cities) 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 carry an umbrella or paint eyes on the back of a hat. Crows rarely attack from the front so having eyes on the back of your head can be an effective deterrent!
Putting all this together to actually find nests, is one of the most rewarding moments an urban naturalist or crow enthusiast can have. Be warned though: crows are wary of potential predators (including people) spying on them and they have a few tricks for throwing you off, so don’t be surprised if a nest location you were certain of turns out to have been a ruse!
Have more questions? Let me know in the comments!