Correlates of Deuterium (δD) Enrichment in the Feathers of Adult American Kestrels of Known Origin

Abstract

Abstract. Many populations of the American Kestrel (Falco sparverius) are in decline; in northern populations it is unknown whether low recruitment and rates of return are due to mortality, poor detection, or dispersal. Ratios of stable hydrogen isotopes in feathers (δDf) have been used widely to estimate origins of birds, in some cases providing estimates of adults dispersal between breeding seasons and post-natal dispersal of young. We attempted to use δD in feathers, grown during breeding, to identify returning and immigrant birds and to quantify dispersal. We used birds of known origin to establish the expected local δDf but found a high degree of deuterium enrichment in these individuals relative to the local δD of rainfall (δDP) and a significant difference between δDf of nestlings and adults, which complicated the distinguishing of local birds from immigrants. We subsequently compared the δD of primary feathers and plasma of adults and tested for relationships among the δD of adult feathers and adu...