No difference in reproductive investment or success across urban and rural breeding pairs in an urban-adapted songbird

Species classified as ‘urban-adapters’ are often assumed to thrive in
cities because they are commonly found across the urbanization gradient.
However, urban-living populations of many urban-adapted species have been
found to have lower reproductive success relative to
their rural counterparts. The European starling (Sturnus vulgaris) is a
common urban-adapted species found across most of the globe; while
starlings have lowered reproductive success in urban areas in their native
range, less is known about how urbanization impacts reproduction in their
invasive ranges. We tested for differences in reproductive investment and
success across urban and rural starling populations in Georgia, which is
part of their North American invasive range. We found few differences in
reproductive output for urban versus rural starlings—clutch size, egg
mass, egg volume, incubation behavior, provisioning rates, brooding
behavior and nestling wing chord were all similar across starling
populations from more urban and more rural study sites. While urban birds
produced a higher number of hatchlings and rural birds produced young in
higher body condition, neither of these factors influenced reproductive
success because the number of fledglings produced were similar for urban
and rural breeding starlings. Overall, European starlings in their
invasive range performed similarly well in more urban versus more rural
habitats. Future work should explore whether urbanization affects other
components of fitness in starlings (e.g., adult survival).