Concrete habitat: Impervious surface and avian fitness decline in two urban adapters

The conversion of natural habitats to impervious surfaces in cities
affects biotic and abiotic attributes of urban ecosystems. Detailed
information on the gradual influence of impervious surfaces on
reproductive output, however, is lacking. Using five years of
nestbox-breeding great tit and blue tit data collected across various
habitat types within and outside a Central-Eastern European capital city,
we quantified the impact of impervious surfaces on avian reproductive
success. Impervious surfaces strongly and negatively covaried with the
number of fledged young in both species: a 0 to 50% increase in impervious
surface within 100 m of the nest was associated with 3.56 fewer fledged
offspring in great tits (95% CI: -4.85, -2.27) and 2.91 fewer fledged
offspring in blue tits (95% CI: -4.26, -1.56), thus halving the
reproductive output of two widespread urban species. These results provide
benchmark values of avian productivity for ecologists and urban policy
makers, and for the management of urban areas.