General mechanisms underlying the distribution and fitness of synanthropic predators in human-influenced landscapes remain unclear. Under the consumer resource-matching hypothesis, synanthropes are expected to distribute themselves among habitats according to resource availability, such that densities are greater in human-subsidized habitats, but mean individual fitness is equal among habitats because of negative density dependence. However, “under-matching” to human food resources can occur, because dominant individuals exclude subordinates from subsidized habitats and realize relatively high fitness. We integrated physiological, behavioral, and demographic information to test resource-matching hypotheses in Steller’s jays (Cyanocitta stelleri), a synanthropic nest predator, to understand how behavior and social systems can influence how synanthropes respond to food subsidies. Jays consumed more human foods at subsidized (park campground) sites than jays at unsubsidized (interior forest) sites based on stable isotope analyses. Jays that occurred at higher densities were in better body condition (based on feather growth bars and lipid analyses), and had greater reproductive output at subsidized than unsubsidized sites. Jays with breeding territories in subsidized sites maintained relatively small home ranges that overlapped with multiple conspecifics, and exhibited a social system where dominant individuals typically won contests over food. Thus, jays appeared to be under-matched to prevalent resource subsidies despite high densities and behaviors expected to lead to resource matching. Our results also indicate that local resource subsidies within protected areas can result in source habitats for synanthropes, potentially impacting sensitive species over broader spatial scales.
Resource matching Synanthropic predators Protected areas Resource subsidies
This is a preview of subscription content, log in to check access.
Funding was provided by Save the Redwoods League, the College of Agriculture and Life Sciences (UW-Madison), the Department of Forest and Wildlife Ecology (UW-Madison), the Office of the Vice Chancellor for Research and Graduate Education (UW-Madison), the U.S. Fish and Wildlife Service, and the California Department of Fish and Wildlife. We thank numerous field and laboratory technicians for their dedicated efforts and California State Parks staff for logistical assistance.
Author contribution statement
EHW and MZP conceived the idea, design, and experiment. EHW performed the experiment. EHW and MZP analyzed the data and wrote the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable institutional and national guidelines for the care and use of animals were followed. The research was conducted under animal ethics permit A01424-0-01-10 and scientific collection permit SC-011200.
The data sets analyzed during the current study are available from the corresponding author on reasonable request.
Fedriani JM, Fuller TK, Sauvajot RM (2001) Does availability of anthropogenic food enhance densities of omnivorous mammals? An example with coyotes in southern California. Ecography 24:325–331CrossRefGoogle Scholar
Fieberg J, Kochanny CO (2005) Quantifying home-range overlap: the importance of the utilization distribution. J Wildl Manag 69:1346–1359CrossRefGoogle Scholar
Fretwell SD (1972) Populations in a seasonal environment. Princeton University Press, PrincetonGoogle Scholar
Fretwell SD, Lucas JS (1970) On territorial behavior and other factors influencing habitat distribution in birds. Theor Dev Acta Biotheor 19:16–36CrossRefGoogle Scholar
Grubb JTC (2006) Ptilochronology: feather time and the biology of birds. Oxford University Press, OxfordGoogle Scholar
Haché S, Villard M-A, Bayne EM (2013) Experimental evidence for an ideal free distribution in a breeding population of a territorial songbird. Ecology 94:861–869CrossRefGoogle Scholar
Hopkins JB, Koch PL, Ferguson JM, Kalinowski ST (2014) The changing anthropogenic diets of American black bears over the past century in Yosemite National Park. Front Ecol Environ 12:107–114CrossRefGoogle Scholar
Horak P, Lebreton J-D (1998) Survival of adult Great Tits Parus major in relation to sex and habitat; a comparison of urban and rural populations. Ibis 140:205–209CrossRefGoogle Scholar
Johnston RF (2001) Synanthropic birds of North America. In: Marzluff JM, Bowman R, Donnelly R (eds) Avian ecology and conservation in an urbanizing world. Kluwer Academic Publishers, Boston, pp 49–67CrossRefGoogle Scholar
Kennedy M, Gray RD (1993) Can ecological theory predict the distribution of foraging animals? A critical analysis of experiments on the ideal free distribution. Oikos 68:158–166CrossRefGoogle Scholar
Kernohan BJ, Gitzen RA, Millspaugh JJ (2001) Analysis of animal space use and movements. In: Marzluff JM, Millspaugh JJ (eds) Radio tracking and animal populations. Academic Press, San Diego, pp 125–166CrossRefGoogle Scholar
Luginbuhl JM, Marzluff JM, Bradley JE et al (2001) Corvid survey techniques and the relationship between corvid relative abundance and nest predation. J Field Ornithol 72:556–572CrossRefGoogle Scholar
Marzluff JM, Neatherlin E (2006) Corvid response to human settlements and campgrounds: causes, consequences, and challenges for conservation. Biol Conserv 130:301–314CrossRefGoogle Scholar
McGowan KJ (2001) Demographic and behavioral comparisons of suburban and rural American Crows. In: Marzluff JM, Bowman R, Donnelly R (eds) Avian ecology and conservation in an urbanizing world. Kluwer Academic Publishers, Norwell, MAGoogle Scholar
Newsome SD, Garbe HM, Wilson EC, Gehrt SD (2015) Individual variation in anthropogenic resource use in an urban carnivore. Oecologia 178(1):115–128CrossRefPubMedGoogle Scholar
Pearson SF, Levey DJ, Greenberg CH, del Rio CM (2003) Effects of elemental composition on the incorporation of dietary nitrogen and carbon isotopic signatures in an omnivorous songbird. Oecologia 135:516–523CrossRefPubMedGoogle Scholar
Peery MZ, Becker BH, Beissinger SR, Burger AE (2007) Age ratios as estimators of productivity: testing assumptions on a threatened seabird, the marbled murrelet (Brachyramphus marmoratus). Auk 124:224–240CrossRefGoogle Scholar
Powell LA (2007) Approximating variance of demographic parameters using the delta method: a reference for avian biologists. The Condor 109:949–954CrossRefGoogle Scholar
Pyle P, Howell SNG, Yunick RP, DeSante DF (1997) Identification guide to North American passerines. Slate Creek Press, Bolinas, CaliforniaGoogle Scholar
R Development Core Team (2014) R: a language and environment for statistical computing. R Foundation for Statistical ComputingGoogle Scholar
Ralph CJ, Droege S, Sauer JR (1995) Managing and monitoring birds using point counts: Standards and applications. U.S. Forest Service, Pacific Southwest Research Station, Albany, CaliforniaGoogle Scholar
Ridley J, Komdeaur J, Sutherland W (2004) Incorporating territory compression into population models. Oikos 105:101–108CrossRefGoogle Scholar
Rodewald AD, Shustack DP (2008) Consumer resource matching in urbanizing landscapes: are synanthropic species over-matching. Ecology 89:515–521CrossRefPubMedGoogle Scholar
Sauer JR, Hines JE, Fallon JE, et al (2014) Breeding Bird Survey Summary and Analysis 1966–2013. Version 01.30.2015. In: USGS Patuxent Wildl. Res. Cent. Laurel MD. http://www.mbr-pwrc.usgs.gov/bbs/bbs.html. Accessed 28 May 2015
Shochat E (2004) Credit or debit? Resource input changes population dynamics of city-slicker birds. Oikos 106:622–626CrossRefGoogle Scholar