American Crow - Photo: Bob Boekelheide
Something to Crow About
by Bob Boekelheide
September 2023
We all know crows, right? We see crows every day in the lowlands of the north Olympic Peninsula, walking on beaches, flying about towns, and cawing on the rooftops. Their reputations range from noisy pests to cunning thieves to smart opportunists.
But do we really know crows? As recently as 2020, birders still thought there were two species of crows in Clallam County – American Crow and Northwestern Crow. Remember the good old days, when we used to say that the crows walking around the schoolyards in Sequim and Port Angeles looked and sounded like American Crows, whereas the crows foraging in the intertidal at Neah Bay looked and sounded like Northwestern Crows? In 2020, that myth came crashing down. Based on genetic information, that year the American Ornithological Society lumped the two species, making the Northwestern Crow a subspecies of American Crow.
The lumping was based on scientific research and a paper entitled “Cryptic and Extensive Hybridization between Ancient Lineages of American Crows,” headed by David Slager. The research showed that American and Northwestern Crows have a “hybrid zone” stretching from southeast Alaska to southwest Washington, centered right here at the Strait of Juan de Fuca and southwestern B.C. In their study, crows at both Neah Bay and Victoria B.C. showed fairly even proportionality in both mitochondrial and nuclear DNA between Northwestern and American types, which means that our Olympic Peninsula crows could not be assigned to one species or the other. Therefore, they are the same species.
The researchers speculated that the Northwestern-type crows split from generic American-type crows when ice sheets advanced during the Pleistocene epoch, within the last few hundred-thousand years. As the ice advanced, Northwestern-types moved into coastal ice-free refugia to the north. When the ice subsequently melted, the two species recombined. This likely happened several times, as continental and coastal mountain glaciers advanced and retreated. Genetically, the study demonstrated that the “hybrids” showed lots of back-crossing, indicating that their crossbreeding may have occurred over many generations, not just recently. Once again, they are the same species.
Close-up of American Crow face – Photo: Bob Boekelheide
If you live in a town on the north Olympic Peninsula, it’s likely that you often see roving bands of crows in your neighborhoods. Depending on the time of year, flocks may be only a few crows, sometimes many more. Crows elsewhere sometimes form giant flocks of thousands of crows (aka “murders”), particularly at communal roost sites, although flocks on the north Olympic Peninsula rarely number more than a few hundred.
The all-time record crow count on eBird, the amazing bird app from Cornell University, occurred in southern Ohio in November 2001, estimated at 500,000 crows. Other communal roosts in the southern plains reportedly held one to two million crows, particularly where migrant flocks mixed with resident flocks. That’s a lot of “caws” for concern. The high count for western Washington was near the UW Bothell campus, where upwards of 20,000 crows may roost together outside the nesting season. The high eBird count for Clallam County is 673, seen by Sue Nattinger near Joyce in November, 2009. As you can see, Clallam crow flocks can’t compare in size with other flocks around North America.
In actuality, the long-term counts of crows throughout western Washington seem to be declining. One measure is our Sequim-Dungeness Christmas Bird Count (SDCBC), occurring every year in mid-December (see Figure 1). The SDCBC shows lots of variability between years, but the average crow count for the last 30 years has declined from just over 1000 crows in the 1990s to just over 800 crows in the last 10 years (Figure 1). Similar trends appear in eBird, which shows an average decline of about 21 percent in relative abundance of crows in the Sequim area between 2007 and 2021.
Since crows are considered very adaptable to humans, why are there fewer crows? One possibility is West Nile Virus, which has caused serious mortality in crows, especially in eastern North America. Another possibility is Avian Influenza, which has spread widely particularly this year, although it seems to affect water birds and raptors more than passerines like crows. The spread of both these viruses is likely enhanced by warming climate and related changes in migratory and nesting patterns of wild birds.
Even though crows are present year-round on the north Olympic Peninsula, data from 20 years of weekly bird walks show that crow numbers in Railroad Bridge Park bump up in the fall, peaking in November (Figure 2). The data also show that fewer crows visited Railroad Bridge Park during the nesting season, from April to September. Crows do not nest within RR Bridge Park, as far as we know, but there are usually several crow nests within a mile or two of the park. Like all corvids, crows are very social, forming structured flocks with a nucleus of older breeding adults. In some ways, crow flocks remind me of wolf packs, centered around older, more experienced individuals.
Crows often target humans and human foods, which perpetuates their reputation for thievery. We have a walnut tree in our yard, where our neighborhood crows tentatively start sampling walnuts about mid-August. The walnuts usually don’t really ripen until September, so in August the first crows taste a walnut or two, then leave. Every few days they land in the tree, as if checking out the ripening crop. Once the walnuts are ripe, look out. Gangs of crows strip walnuts out of the tree and pick fallen walnuts off the ground, prying them apart with their bills or dropping them in the road to open them. Any suitable platform becomes a walnut-pounding zone, be it a telephone pole or neighborhood roof. Clumsy crows drop walnuts off the roofs into the gutters, to our great consternation. We laugh about it now, but one year my neighbor’s gutter totally plugged up and spilled water on their porch during the first big rainstorm of the fall. They dismantled the gutter and found it was totally crammed full with walnuts. Sorry, neighbors!
American Crow perched on baby stroller. Photo: Bob Boekelheide
It turns out that some crow populations migrate, particularly those that nest in areas of Canada and the northern U.S. where winter conditions can be downright nasty. It is likely that nesting crows on the Olympic Peninsula do not migrate, but are instead resident year-round. In this regard, it would be most interesting to know how far our resident crows range during the year. Do they stay close to their nesting areas, or do they move around the peninsula? Might other crows migrate through the north Olympic Peninsula, possibly interacting with resident populations and increasing local numbers in fall? This seems unlikely, considering that crows do not have the propensity to fly over huge stretches of open water.
Research shows that during the nesting season many breeding pairs are joined by other crows that help by bringing food to incubating females and chicks, and by chasing off predators. These “helpers” are usually offspring from previous years, but not always. Research with marked crows reveals that sometimes helpers are not related to breeding pairs, but they’re still tolerated around the nest. Since crows do not start nesting on their own until they are at least two-years-old and often older, the extra years with experienced breeders might provide critical training to prepare young birds for successful nesting later in life.
Crows usually build a big stick nest placed in either a conifer or a deciduous tree. Look for crow nests after the deciduous trees have lost their leaves in the fall; they can be difficult to find when the trees are still in leaf. Female crows do most of the nest building, weaving sticks in place to their satisfaction. They occasionally reuse nests, but most of the time they build new ones. Other species such as hawks, owls, sleeping raccoons and squirrels often use abandoned crow nests.
Crows’ typical clutch sizes averages four to five eggs, ranging from three to six eggs. The eggs usually have a blue or greenish background color covered with dark smudgy spots. The female does all the incubation, fed by the male and any helpers at the nest. The eggs typically hatch in 16 to 18 days. Crows then go through an extensive chick and fledgling period, not leaving the nest until about 30 to 35 days after hatching, then not leaving their nest tree for several more days after that. They remain dependent on their parents for food for several more weeks, begging raucously and persistently starting at the crack of dawn. I once made the mistake of camping below a crow’s nest with several fledglings, which started their nasal “AAHH, AAHH, AAHH, AAHH…” non-stop begging about 4:30 in the morning. No more sleep for me. But the best thing about fledgling crows is their striking blue-eyes, which quickly turn brown during their first year.
American Crow fledgling showing its blue eyes. Photo: Bob Boekelheide
It’s not an easy life being a crow. Research with banded crows showed that more than half the chicks that made it to fledging died within their first year. Less than 10 percent of marked birds made it to five years old, and almost no adults lived beyond eight years. Despite this, the longevity records for banded crows are 15 to 17 years old. Very few crows ever make it to these ripe old ages.
When I first moved to Sequim in the 1990s, in late summer I noticed flocks of crows flying together at dusk into the foothills of the Olympics, apparently going to a roost site. Over a few evenings I stationed myself at various places, hoping to track where the crows ended up. The best I could do is follow them up the Dungeness River valley to an area near Slab Camp, at about 2500 ft elevation. Unfortunately, I never found the exact roost site. Suffice it to say, they traveled several miles into the Olympic foothills to find a roost with the right conditions. Secretive little devils.
At the time I worked at Sequim High School, where football games occurred some Friday nights. One early Saturday morning, after a football game the night before, I happened to be at school right at dawn and found a big flock of a hundred or so crows already walking around the football field, foraging on food scraps littering the stands and field. My guess is these crows knew exactly when football games occurred and made it a point to arrive early the next morning for spilled food and tasty morsels.
Look deep into the eyes of wild crows. They have the true spark of life, totally observant and aware of their surroundings. Here is your homework assignment: Go watch a flock of crows this month and really observe how they behave and interact with one another and the rest of the world. Then think about the walnuts in my gutters.
Many of the interesting facts about American Crows in this story came from Birds of the World, an on-line resource available through Cornell Lab of Ornithology. I highly recommend that all bird aficionados get an online subscription to Birds of the World, both for its wonderful information and to support the Lab of Ornithology.