Purple Martins First Flights



A. Principal Investigator

Dr. Heather Williams, Clinical Assistant Professor, State University of New York at Buffalo
Email: ;
Mail: Department of Biological Sciences, 109 Cooke Hall, University at Buffalo, North Campus, Buffalo, NY 14260

B. Introduction

Purple martins (Progne subis) are native migratory cavity-nesting insectivores with regionally declining breeding populations (Tautin et al. 2008). A substantial body of work has focused on the nesting stage of the lifecycle in this species and has addressed questions such as the effect of nest ectoparasites on nestling health (Williams, Dittmar and Smith Pagano, 2020); the importance of managed housing for nestling success (Raleigh et al. 2019) and the factors affecting incubation attentiveness (Williams and DeLeon, 2020a) and provisioning rate (Williams and DeLeon, 2020b). It is much harder, however, to study what happens to these nestlings once they fledge the nest. This knowledge gap is especially problematic given that the post fledging stage (particularly prior to initiation of autumn migration) is associated with the highest mortality risk in many migratory species (Vitz and Rodewald, 2011).

Recent advances in wildlife tracking technologies are making it easier to monitor and research even small-bodied juvenile birds such as purple martins. Tag transmitters are now light enough to be safely carried by small-bodied birds and have the battery life to transmit data for more than 1 year without the need to recapture the individual. Crucially, the growth in uptake of the Motus Wildlife Tracking System has made intermittent tracking of individuals possible on a continental basis at a relatively low cost (Taylor et al. 2017). Motus is an array of automated radio telemetry stations which can track movements of small animals. Locations of animals fitted with a tag transmitter are recorded whenever they are within range of a receiving station (Figure 1).

The goal of this project is to use a combination of automated radio-tracking through the Motus system and manual VHF radio tracking to gather data on purple martin juvenile survival, habitat use and migration departure date. We plan to link this new data on the juvenile stage to our previous work looking at the level of parental care nestlings receive in the nest (Williams and DeLeon, 2020a; Williams and DeLeon 2020b) and nestling body condition (Williams, Dittmar and Smith Pagano, 2020). This combined approach will allow us to consider how events in the nest affect success of birds beyond the nest i.e. whether there is a carry-over effect from nesting to the post-fledging stage, to the early stages of autumn migration.

While this question has never been addressed in purple martins, previous work in Ontario with nestling barn swallows (Hirundo rustica) found that nestling body condition was a strong predictor of survival at the post-fledge stage and that birds fledged earlier in the season also initiated migration earlier (Evans et al. 2020). This previous work used a measure of nestling body mass scaled by structural size as a relatively simple measure of nestling body condition. We plan to build on this result in a new species by incorporating more in depth measurements of body condition including using artificial intelligence analysis of nest video footage to quantify in-nest provisioning rate and incubation attentiveness.

The secondary goal of this project is to better understand the localized movements of purple martin fledglings around the breeding ground prior to migration initiation. We plan to use handheld VHF tracking around our field site to gather high resolution location data from which we can deduce habitat preferences (Boynton et al. 2020).

The post-fledge stage is the least well studied stage in the lifecycle of most migrant birds, and the stage which entails the highest mortality. This project aims to make a substantial contribution to our understanding of this life stage for a native cavity nesting species of conservation concern.

C. Project Motivation

Hypothesis: The level of parental care (and thus nestling condition) will affect post-fledge survival and migration departure date in purple martins, with nestlings experiencing higher provisioning rate having a better pre-fledge body condition and having a higher post-fledge survival rate and earlier migration departure date than nestlings experiencing a lower level of parental care. Secondarily, we also plan to assess habitat use in post-fledgling purple martins.

Relation to NABS mission: This work concerns a native cavity nesting bird which is experiencing regional population declines (the purple martin). The post-fledging stage is thought to entail the highest mortality rate in the lifecycle, and so research addressing this stage has not only an academic, but also a conservation value.

NOTE: If additional information on this grant is desired, please contact Jim Engelbrecht via email at