Shoreline Area Wildlife: Crows

Thursday, April 21, 2011

Crow. Photo courtesy PAWS

PAWS provides regular posts about wild animals commonly found in the Shoreline-Lake Forest Park area. Each post gives facts on the species’ natural behavior, as well as how to avoid and resolve common problems with the animals. 
Crows are among the world's most adaptable and intelligent birds. For example, crows are able to recognize individual human faces, solve simple problems and use simple tools. Watch this example. They have evolved a varied language, and are capable of mimicking sounds they hear, including other animals. They also learn to associate noises with specific events, especially with food distribution.
Habitat and food
Crows live in diverse habitats across North America. They thrive close to humans in cities and suburbs. They roost at night in large flocks of up to several thousand during the winter. During the day, smaller groups may fly up to 50 miles in pursuit of food.
With a preference for coniferous trees like firs, crows build their nests in woods or isolated trees at least 60 feet above ground. Nests are solidly built of branches and twigs and are lined with bark, plant fibers, mosses, twine, and other found materials.
As omnivores, crows eat whatever is available, including insects, small amphibians and snakes, earthworms, eggs, nesting birds, and saltwater invertebrates such as clams and mussels. They also scavenge dead animals and garbage and eat wild and cultivated fruits and vegetables.
Crow.  Photo by Quinet.
 Nesting and population
Paired male and female crows together incubate their four to six eggs, which hatch in 18 days. The young first fly when they are about one month old. Frequently at least one young bird will remain with her parents through the next nesting season to help care for the new nestlings, by bringing them food and guarding the nest.
In recent years, crow populations have expanded in urban and suburban areas in the Northwest. Wildlife biologists suggest that the increase will soon level off. Although crows can find unlimited food sources, they have begun to run out of potential nesting sites.
Solving and preventing conflicts
Crows have survived centuries of efforts by humans to eradicate them. They have been shot, poisoned, and bombed, but they have endured and even expanded their range.
Common complaints about crows include:
  • Eating corn and other crops.
  • Raiding garbage cans.
  • Dive-bombing people during nesting season.
Most people may not know that crows can actually benefit agriculture by eating insects and larvae that damage crops.
Crow-proof your home
Crows are attracted to food scraps in garbage cans and compost piles, and easy pickings in gardens. Make it as hard as possible for them to raid.
  • Dispose of trash in secure cans with tight-fitting lids.
  • Secure lids further with a bungee cord or chain, or store in a locked shed.
  • Do not put food of any kind in open compost piles.
  • Bury food in an underground composter or put it into a lidded worm box (read more about composting from Seattle Tilth).
  • Avoid feeding cats and dogs outdoors. If you must, pick up bowls, leftovers and spilled food as soon as pets have finished eating.
  • Protect trees and shrubs with bird netting, which can be purchased in a variety of sizes at garden and hardware stores. Tie the netting securely at the base of the plant or on the trunk of the tree to prevent birds from gaining access from below. Harvest crops immediately as they ripen.
  • Crows are particularly fond of young corn plants. As soon as corn has been planted, protect germinating plants with a row cover until they are about eight inches tall.
Flying crow. Photo by John-Morgan.
Avoid dive-bombers
While crows have young in the nest and on the ground learning to fly, they may defend their nesting territory by dive-bombing other animals and people. This territorial behavior is only temporary and will quickly subside as the young fledge from the nest and learn to fly. If possible, it is best to stay away from nesting areas until the young have fledged and the parents are no longer as protective.
Dive-bombing crows are using intimidation to keep what they think is a potential threat away from their young. They rarely hit their targets. If entering the crow's nesting territory is unavoidable, carrying an open umbrella will keep the protective parents from coming too close.
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