Crow population increases in Santa Cruz – Santa Cruz Sentinel

SANTA CRUZ — For the past few years in the city of Santa Cruz, between August and February, mass murders (flocks) of crows span the skies and caw from the trees, whether on their way to hunt for feed during the day or on their way. way back to their dorms in the evening.

“During fall and winter, crows are less territorial and form large, noisy flocks that roost together at night,” said Santa Cruz-based avian researcher and biological consultant Alex Rinkert. “They are often encountered in herds during the day as well as at this time of year relative to the breeding season when they are more territorial.”

Longtime residents of the city may have noticed the crow population increasing in recent decades as non-native birds have discovered an endless feast of trash and leftover food to feast on, according to Rinkert.

“The crow population in Santa Cruz has increased dramatically over the past 30 years and has shown no signs of leveling off,” he said. “Before this expansion, crows were very rarely encountered in Santa Cruz. The crow population in Santa Cruz today is hundreds of times larger than it was historically. Human-made food subsidies in the form of garbage cans open, pet food bowls and direct feeding by people are contributing to this population explosion.

Santa Cruz crows, which now number in the thousands, exhibit behaviors not found in other areas and have adapted to the coastal city in ways that remain a mystery to researchers.

“Their breeding season begins in February when the adults collect twigs and greenery for their nests, and ends in mid-June when the last nests fledge,” Rinkert said. “During the breeding season they are very territorial but in the fall and winter they are much more gregarious and form large flocks that descend on quarters and roost sites in the evening. The crows, as well as other species of corvids, have complex social behaviors that scientists are still trying to understand.

Being a non-native species in Santa Cruz, increasing crow killings are having a negative impact on native animals that already face so many threats in the urban environment.

“As predators, they have a profound impact on native animal populations,” Rinkert said. “People know their predilection for trash best, but they also actively hunt and catch a wide variety of native animals. Not only are they detrimental as predators, but they also harass hawks and owls, sometimes relentlessly, which can make it more difficult for these species to exist in urban areas.

Crows have no natural brake in the local ecosystem and because of this, the population will continue to grow more and more for the foreseeable future.

“Raptors, mammals, and vehicles may choose one from time to time, but these mortalities have virtually no effect on the population,” Rinkert said. “At some point there will be more crows than food resources and breeding grounds, which will slow population growth, but I think that’s still in the distant future.”