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What's New

A comment about calls. We occasionally include a characteristic noise for the species other than a call in this category, such as wing noise for mourning dove. Several users have questioned these noises. However, we did mean for them to be included!

The following changes have been made to the infocenter in response to the latest AOU checklist supplement (AOU Check-list Supplement. (2000). The Auk 117(3):847-858.):
  • Oldsquaw changed to Long-tailed Duck
  • Caracara plancus changed to Caracara cheriway
  • Genus Catharacta changed to Stercorarius
  • Strickland's Woodpecker (Picoides stricklandi) changed to Arizona Woodpecker (Picoides arizonae)
  • Pica pica changed to Pica hudsonia
  • Poecile atricapillus, hudsonicus, and cinctus have "us" ending changed to "a"
  • Baeolophus griseus changed to B. ridgwayi
  • Bullock's Oriole moved to after Hooded Oriole
  • 2 species added: Nazca Booby (split from Masked Booby) and Gunnison Sage-Grouse (split from Greater Sage-Grouse). For more information on the splits see:

    Young, J.R., Braun, C.E., Oyler-McCance, S.J., Quinn, T.W., Hupp, J.W. (2000). A new species of Sage Grouse (Phasianidae: Centrocercus) from southwestern Colorado, USA. Wilson Bulletin 112: In Press.

    Pitman, R.L., Jehl, J.R. (1998). Geographic variation and reassessment of species limits in the "Masked" boobies of the eastern Pacific Ocean. Wilson Bulletin 110:155-170.

    Roberson, D. (1998). Sulids unmasked: Which large booby reaches California? Field Notes 52:276-297.

Has the Infocenter changed?

Due to technical difficulties, the infocenter is not entirely functional at this time. We apologize for the inconvenience and we are working to restore the information. Information that is missing that was once part of the infocenter includes incubation time, printable fact sheets, reader's forum, and animated maps.

Length and Wingspan

"The measurements of total length are original figures based on actual field measurements, from the tip of the bill to the tip of the tail, of thousands of live birds hand-held in natural positions. These live measurements are shorter than conventional ones (of dead birds, stretched "with reasonable force"). The single figure given for length is a median or average figure for the adult male, rounded to the nearest 1/4 inch in small birds and to the nearest 1/2 inch or 1 inch in larger birds. Individual birds may be 10 percent larger or shorter. Thus a bird recorded as 10 inches may be between 9 and 11 inches. On larger flying and soaring birds an average wingspan measurement also is given."
Robbins, C.S., Bruun, B., Zim, H.S., (1966). A Guide to Field Identification: Birds of North America. New York: Western Publishing Company, Inc.

Question marks after a number indicate that the species name has changed due to a split or lump after the reference was published and the measurements do not necessarily pertain to the new species. A dash indicates a range of measurements for the species indicating some variation among subspecies.


The egg images were taken by Gregory Gough using a digital camera. The collection is from P.C. Isbell and was donated to the Patuxent Wildlife Research Center.

Egg length from: Baicich, P.J., Harrison, C.J.O., (1997). A Guide to the Nests, Eggs, and Nestlings of North American Birds. San Diego, CA: Academic Press.

Clutch size, days to fledge, length of incubation and number of broods

A question mark indicates uncertainty and a dash indicates a range of values. Plus (+) and greater-than (>) signs indicate more. The first number, if followed by a range in parentheses, indicates what is typical, the range shows the variability observed.

From: Ehrlich, P., Dobkin, D., Wheye, D., (1988). The Birder's Handbook: A Field Guide to the Natural History of North American Birds. New York: Simon and Schuster Inc.

Migration status, breeding habitat, nest location and nest type

Birds are grouped by their common attributes. More information can be found at: http://www.mbr-pwrc.usgs.gov/bbs/guild/infogrp.html


Peterjohn, B.G., and J.R. Sauer, (1993). North American Breeding Bird Survey annual summary 1990-1991. Bird Populations 1: 52-67.

A discussion of some of the problems with group summaries is in:

Sauer, J. R., G. W. Pendleton, B. G. Peterjohn, (1996). Evaluating causes of population change in North American insectivorous songbirds. Conservation Biology 10:465-478.

Last updated on July 24, 2000.
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