Biology Reference
In-Depth Information
The Effects of the Environment on Birds
Q How are birds affected by climate change?
A
Climatechangeisinfluencingtheabundance,distribution,andtimingofmigrationand
breeding for many species. So far various climactic changes have helped some species,
harmed others, and had little effect on the rest. A recent study by the National Audubon
Society showed that more than half of the birds commonly found on the Christmas Bird
Count are wintering farther north now than they did 40 years ago.
AmericanRobinsarenowarrivingapproximately14daysearlierthantheydidin1981
on their breeding grounds in the Colorado Rocky Mountains. Tree Swallows have ad-
vancedtheirbreedingdatebyupto9daysearlier from1959to1994.Red-winged Black-
birds, Eastern Bluebirds, and eastern populations of Song Sparrows now lay their eggs
earlier because spring temperatures are warmer.
In addition to these effects on migration and breeding, birds are at risk from habitat
changes caused by climate change, especially on the tundra, in alpine meadows, on sea
ice and glaciers, in coastal wetlands, marine atolls, and oceans.
These species may face severe conservation challenges in the coming decades. Sea
level rise may inundate islands, jeopardizing nesting birds. The potential spread of
mosquito-borne avian malaria to highlands where the surviving Hawaiian honeycreepers
have retreated is also a danger.
In the future, climate change is expected to affect the survival and reproduction of
many bird species. Again, changes are expected to benefit some species and harm others.
Changes in prey distribution and abundance, shrinking habitats, and changes in rainfall
and water availability are expected to present great challenges to some birds on land and
at sea.
Eastern Bluebirds occur across eastern North America and south as far as Nicaragua.
Bluebirds living in the more northern and western parts of the range usually lay more
eggs than dothe more eastern and southern birds. Eastern Bluebirds typically have more
than one successful brood per year. Young produced in early nests usually leave their
parents during their first summer, but young from later nests frequently stay with their
parents through the winter.
