Contents
On Measuring Bird Habitat: Influence of Observer Variability and Sample Size
William M. Block, Kimberly A. With, and Michael L. Morrison
Day-to-day Variation in Nest Attentiveness of White-rumped Sandpipers
Ralph V. Cartar and Robert D. Montgomerie
Microgeographic Song Variation in the Nuttall's White-crowned Sparrow
Michael A. Cunningham, Myron C. Baker, and Thomas J. Boardman
Present Status of the Flightless Cormorant, Galapagos Penguin and Greater Flamingo Populations in the Galapagos Islands, Ecuador, After the 1982-83 El Nino
Carlos A. Valle and Malcolm C. Coulter
A Field Study of Winter Fruit Preferences of Cedar Waxwings
Jean M. Mcpherson
A Comparative Study of Eggshell Thickness in Cowbirds and Other Passerines
Carol D. Spaw and Sievert Rohwer
Determinants of Nestling Feeding Rates and Parental Investment in the Mountain Chickadee
Ralph Grundel
Effects of Body Condition on Molting in Mallards
Olof Pehrsson
Factors Influencing Colony Attendance by Pigeon Guillemots on Southeast Farallon Island, California
Douglas A. Nelson
Bird Visitation to Agave Salmiana; Comparisons among Hummingbirds and Perching Birds
Carlos Martinez Rio and Luis E. Eguiarte
Intraclutch Variation in the Size, Mass and Composition of Ring-billed Gull Eggs
Catherine E. Meathrel and John P. Ryder
Egg Data Slips-are They Useful for Information on Egg-laying Dates and Clutch Size?
Douglas B. Mcnair
Nest Site Selection by Northern Goshawks in Northern New Jersey and Southeastern New York
Robert Speiser and Thomas Bosakowski
Genetic Variation, Population Structure, and Evolution of California Quail
Robert M. Zink, Dale F. Lott, and Daniel W. Anderson
Breeding Vocalizations Ofthe Surfbird
Edward H. Miller, William W. Gunn, and Stepthen F. Maclean Jr.
Book Reviews
March F. Lawton
Books Received
The Condor
News and Notes
The Condor
Covers
Back Matter (PDF)
The Condor
Front Matter (PDF)
The Condor
Commentary
Personal Perspectives and Lack of Data Underlie Different Interpretations of Interspecific Aggression
Bradley C. Livezey
Short Communications
Aggressive Encounters Between Tundra Swans and Greater White-fronted Geese during Brood Rearing
Craig R. Ely, David A. Budeau, and Una G. Swain
Geographic Variation in Social Structure and Behavior of Aphelocoma Ultramarina
Stuart D. Strahl and Jerram L. Brown
Metabolic, Water and Thermal Relations of the Chilean Tinamou
Philip C. Withers, Richard B. Forbes, and Michael S. Hedrick
Revised Breeding Distribution of the Boreal Owl in the Northern Rocky Mountains
Gregory D. Hayward, Patricia H. Hayward, Edward O. Garton, and Ronald Escano
First North American Nesting and Occurrence of Haliaeetus Albicilla on Attu Island, Alaska
Theodore G. Tobish Jr. and Lawrence G. Balch
Cone Pigment of the Great Horned Owl
Gerald H. Jacobs, Michael Crognale, and John Fenwick
Amino Acid Composition of the Calamus, Rachis, and Barbs of White-crowned Sparrow Feathers
James R. King and Mary E. Murphy
Effects of the 1982-83 El Nino Event on Blue-footed and Masked Booby Populations on Isla Daphne Major, Galapagos
H. Lisle Gibbs, Steven C. Latta, and James P. Gibbs