| I studied least bittern (Ixobrychus exilis) breeding biology and the effectiveness of call-response surveys for monitoring least bitterns at Iroquois National Wildlife Refuge and Oak Orchard and Tonawanda State Wildlife Management Areas, New York. I tracked 33 adults and 12 chicks via radiotelemetry and did call-response surveys on 15 radiomarked males. Mayfield success rates averaged 48.15% and birds both renested and had double broods. Adult home range averaged 9.7 ha (n = 33), and chicks averaged 13.4 m from nests before 23 days old (n = 11). Vegetation structure and composition and marsh size should be considered when managing for populations. Broadcasting conspecific calls increased calling compared to passive listening, and response to broadcasts was highest around nest initiation. Call-response surveys are an effective monitoring tool, but surveys should be done when most birds are initiating nests. Response rates can be used to estimate true abundance of males. |
