Range maps should be used with the understanding that they provide only a general indication of typical distributions. Ranges are highly variable for many species and are very dynamic. Range maps are static and usually several years behind the birds. These are some of the complications that present themselves when developing range maps.
Summer or winter range information may hide migration pathways.
Ranges of some species can vary from year to year.
Warmer winters are changing historical ranges. As an example, the White-winged Dove, common in south Texas but once very rare in North Texas, is now common at many feeders on a year-round basis in North Texas. Red-bellied Woodpeckers are spending their winters much further north than in the past.
Populations of some species can be high in a specific area one year and totally absent the next (irruptive behavior).
Ranges of some species are expanding very rapidly. The Eurasian Collared-Dove is an introduced species that has quickly moved from its initial introduction in Florida to much of the United States. Its range is expanding faster than updated range maps are being produced.
Other species expand their ranges after nesting. A great example is the Cattle Egret. Its winter range is Mexico, southern Texas and along the coast to southern Florida. Its nesting range includes most of Texas, east to South Carolina. After nesting, Cattle Egrets will disperse to large parts of the United States and even into southern Canada. The range of Cattle Egrets after this post-nuptial wandering is widespread and very irregular. At the end of the summer the egrets will then migrate from their widespread late summer and fall homes to their winter locations.
Report your sightings Help develop accurate distributional information by reporting your sighting of the American Goldfinch to eBird.
In the Field
Range maps in field guides vary as much as actual bird distribution. Take two different field guides, select 20 images at random, and compare the range maps. You might be surprised by the differences in the ranges shown.
The Professor's favorite field guide for range maps is the Kenn Kaufman Guide to Birds of North America. Here are the Professor's picks for the best field guides.
Best Range Maps Kenn Kaufman's Guide to Birds of North America Click here to order. $18.95 Special offer: $17.50
Best for Birders in the Field National Geographic Field Guide to the Birds of North America Click here to order. $23.95 Special Offer: $21.95
Best Overall Resource The Sibley Guide to Birds Click here to order. $34.95 Special Offer: $31.45
Best for the Backyard The Stokes Eastern or Western Guides Click here to order the eastern guide. $18.95 Click here to order the western guide. $18.95
The Birds of North America web site has excellent distribution information, annual membership required.
Visit the eBird web site to report sightings of the American Goldfinch and to view current and some historical information on a state-by-state basis. Information based on reports from birders in the field.
NatureServe provides information on birds and other wildlife.