Winter cold and bird migration
Some of our early migrating birds like robins, killdeer, and meadowlarks are returning to the area only to be assaulted with very cold temperatures. One wonders how these early arrivals are faring. Fortunately many of our early arrivals are larger birds that generally have more fat reserves and have the ability to cope with changing environmental conditions.
Birds like robins have a diverse diet and they can make due with what is available. Smaller insectivorous birds on the other hand have less energy reserves and are more dependent on locating specific foods such as insects, so the timing of their arrival is more dependent on having plenty of food available. Some returning migrating birds have been assaulted with cold temperatures this year. If some of these more specialized feeders arrive to winter conditions, they do not survive very long. Fortunately, temperatures and wind currents play important parts on the timing of migration. If the wintering grounds are experiencing colder conditions, hormones found in the bird that trigger the urge to migrate might develop slower helping to prevent early departure.
Also, prevailing strong winter winds such as the now popular Polar Vortex produce headwinds that ground birds or tire them to the point that they need to spend some time refueling with food and water before they once again can begin their journey.
Many of these birds will stay in place until the prevailing winds shift to the south before again taking flight. Nonetheless, migration is one of the more dangerous times in a bird’s life and some estimate that 30 percent or so of migrants perish on their journey. Despite the peril, switching location for better conditions during the winter and summer months is better for the survival of the individual species as a whole. You may have seen robins overwintering in our area. They may be birds that came to our area from New England or Canada; they will return to the north before long. The cold doesn’t bother them with their downy insulation and their ability to produce heat by shivering. The lack of insects and worms in the winter is another matter.
They eat fruit and berries all year, but in the winter are restricted mainly to a diet of berries, eating the fruits and berries of crabapple, holly, mountain ash, chokeberry, sumac, hawthorn and juniper. If you have a heated birdbath, you have probably seen robins drinking from it even in the coldest weather. With food and water, they have a good chance of surviving until spring.
Nature Note for 3/23/2014