Black Swift Statewide Monitoring in Colorado: 2022-2023 Report

Sparks, Rob; Latif, Q; Rossi, L

The northern Black Swift (C. niger. borealis) is a cryptic species of significant continental conservation concern, having experienced range-wide population declines in the US and Canada. There is an urgent need to estimate abundance both state-wide and more broadly across this species range. A lack of accurate baseline data on abundance, population size, trend, and habitat associations are currently limiting our ability to develop effective management and conservation plans for this species. Effective management of wildlife populations requires reliable estimates of population status to determine threats and identify areas of conservation importance. Understanding a species population status is especially relevant for threatened or declining species that are of high conservation concern. Survey protocols and study designs that incorporate spatial variation and detectability substantially improve data quality for evaluating management and informing conservation decisions. Our goals were to develop a sampling design and evaluate factors influencing detection probability and abundance. We developed a sampling protocol and design that accounts for Black Swift spatial variation and detection probability. To assist with conservation planning we developed a site assessment map and management recommendations. In 2022 and 2023 we estimated a mean of 7.86 – 6.87 individuals across surveyed sites and estimated 937 and 891 birds respectively across the 476 known potential nesting sites within the state of Colorado. Together, the amount of flowing water, extent of potential nest niche shade, aerial access, amount of potential nest niches, degree of relief and amount of moss increased abundance significantly, providing evidence that these habitat characteristics are important for predicting colony size. We found geographical differences in Black Swift abundance with higher abundance in southern sites compared to northern sites. Detection probability increased before sunrise and after sunset coinciding with their crepuscular flight behavior. Detectability was similar between morning and evening surveys, increasing to 34% during twilight hours. Thus, we consider conducting surveys during twilight hours important for meaningful detectability. Our monitoring design establishes a repeatable sampling frame and standardized protocols to account for spatial variation and detection probability and lays the groundwork for understanding population dynamics.