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Black capped and mountain chickadee nestling fecal samples

Citation

Grabenstein, Kathryn (2022), Black capped and mountain chickadee nestling fecal samples, Dryad, Dataset, https://doi.org/10.5061/dryad.qfttdz0kc

Abstract

Urban and suburban ecosystems are growing in size and number as the human population continues to increase. Not all cities are built the same, however, and it is still unclear how resident organisms are faring in increasingly urban habitats and whether cities are ecological sinks. To investigate how urbanization is affecting breeding success in insectivorous birds, we studied two species of chickadee, the black-capped and mountain chickadee[KG1] , along an urban-rural gradient in Boulder County, CO, USA. We used a citizen-science based experimental framework of nest boxes installed on private land throughout Boulder, CO, USA to local monitor breeding populations of chickadees relative to urbanization. Black-capped and mountain chickadees are two species of closely-related songbirds that co-occur broadly along an elevational gradient. Black-capped chickadees are considered to prefer nesting in low-elevation deciduous trees typically found in cities, while mountain chickadee prefer higher elevation, coniferous forests often considered more rural. However, both species do nest in relatively urbanized habitats, but little is known about how they are navigating these urban habitats. Using arthropod surveys & eDNA metabarcoding paired with field observations, we sought to determine if there are species differences between 1) how chickadee nestling condition varies with the level of urbanization of a nesting site and how urbanization of a nest site infleunces 2) insect availability, 3) nestling diet, and 4) adult provisioning effort. We found that there was no significant effect of urbanization on nestling condition in either species, and that urbanization did not significantly predict insect availability, nestling diet, or adult provisioning effort. We did detect however, differences in diet between the species, highlighting clear ecological niches between these species, despite overlapping breeding habitat. This is, to our knowledge, the first study documenting discrete ecological niches in prey preference for developing chicks and adds to a growing body of literature detailing ecological differentiation between these two species. How this divergence in diet contributes to these species ability to navigate increasingly urban habitats is less clear. It is likely that Boulder, Colorado is made of vegetation patches, effectively urban forest fragments, that allow chickadees living in the city to reproduce successful despite decreased prey quality and quantity associated with urban spaces.

Funding

National Science Foundation