Microhabitat Selection and Singing Behavior Patterns of Male House Finches (Carpodacus mexicanus) in Urban Parks in a Heavily Urbanized Landscape in the Western U.S.

by Esteban Fernández-Juricic, Rachael Poston, Karin De Collibus, Timothy Morgan, Bret Bastain, Cyndi Martin, Kacy Jones, and Ronald Treminio

Department of Biological Sciences, California State University, Long Beach, 1250 Bellflower Blvd., Long Beach, CA 90840-3702.

Abstract

We assessed the role of park size, habitat structure, human disturbance (pedestrian rate and ambient noise), and the number of conspecifics in the distribution, spacing, and singing behavior of male house finches (Carpodacus mexicanus) in urban parks in south Los Angeles County and north Orange County, California. We found that the probability of house finch males occupying urban parks increased with park size and tree structure (total tree cover, tree height, and the number of stems 30 to 50 centimeters in diameter)—two features that may increase the availability of suitable nesting substrates. Nearest neighbor distance between singing males increased with denser vegetation structure (e.g., number of stems), probably because of better nesting and foraging resources or greater availability of protective cover, which would reduce grouping. Males increased their singing rates in the most exposed parts of their perches (upper and outer portions). They also raised the low frequency of their songs to reduce the masking effects of high levels of ambient noise. However, the number of notes per song decreased with ambient noise, and since females are attracted to long songs, this could decrease mating opportunities. Our results point out some of the mechanisms house finch males use to increase their breeding success in urbanized areas and indicate that this success may vary depending on the specific spatial location of nesting areas within a city.

Key words: ambient noise, birds, distribution, house finch males, spacing behavior, singing rate, songs, urban ecology, urban parks