Florida sandhill crane survival along a wildland-to-urban land use gradient

Abstract

The Florida sandhill crane (Antigone canadensis pratensis) is a state-threatened non-migratory subspecies. Our understanding of adult crane survival in Florida, USA, is unclear, as it relies on decades-old unpublished data of birds residing in natural areas. Since that time, the loss of natural habitat precipitated cranes using urbanized areas such as suburban lawns and roadside verges for foraging and loafing. Contemporary studies are needed to properly guide crane management and conservation efforts. We addressed this knowledge gap by estimating the annual survival rate for sandhill cranes in 12 central Florida counties. We used a live-dead capture-recapture multistate model, monitoring 118 adult cranes from June 2017 to May 2023; 76 were color-banded and 42 were tagged with Global System for Mobile Communications (GSM) transmitters. Fifteen cranes died during the study, with vehicle strikes (n = 9) being the most prevalent identified source of mortality. Overall, the annual survival probability was estimated at 0.79 (95% credibility interval = 0.75–0.84). Using the subset of GSM-tagged cranes, we observed no influence of urbanization on annual survival rate (β_{urbanization gradient} = 0.007, 95% credibility interval = −0.008, 0.022). The adult survival rates we observed are lower than reported for other populations of sandhill cranes in North America that are considered stable or growing.