Eastern Bluebirds (Sialia sialis) rear four broods to apparent fledging in northeastern Arkansas

Abstract

Climate change has advanced the onset of spring and, subsequently, avian nesting activity. Although this advance can have negative consequences such as phenological mismatch, species may be able to increase the annual number of young fledged. Eastern Bluebirds (Sialia sialis) can rear 3 broods to fledging, but in this paper we report 3 pairs that reared 4 broods to apparent fledging in 2016 and 2020 in northeastern Arkansas. Nesting attempts began as early as 18 March with the first laid egg and concluded as late as 18 September with the last fledging event; brood sizes ranged from 2 to 5 chicks. Nests were checked daily 15–18 d post-hatching, increasing confidence in our determination of successful fledging. Unlike a previous report of 4 broods reared by a male that mated with 2 females at once, the pairs at our site all remained together through all 4 attempts. These pairs all consisted of after-second-year birds and we discuss why we believe these nests were successful, as well as factors that allowed these pairs to attempt to rear an additional brood.