Methods:
During summer 2024, I will affix approximately 90 tags to the following songbird species, representing seven species across four families: Vireo olivaceus (Red-eyed Vireo),Catharus fuscescens (Veery), C. guttatus (Hermit Thrush), C. ustulatus (Swainson’s Thrush), Setophaga coronata (Yellow-rumped Warbler), Junco hyemalis (Dark-eyed Junco), and Zonotrichia albicollis (White-throated Sparrow). These species were selected because they are abundant breeders locally and across North America, are large enough to carry the smallest geolocation tags, and have large geographic ranges such that geolocation will greatly improve our understanding of migratory distance of specific populations. These tags will comprise a combination of Intigeo dual pressure-light tags, and Lotek PinPoint-10 GPS tags, depending on the mean mass of each species — both of which have different advantages. Dual pressure-light tags are lighter and can be affixed to smaller birds, and incorporate atmospheric pressure data, but are constrained in their longitudinal accuracy by their reliance on sunlight timing. GPS tags offer much more accurate positional data, but are too heavy for all study families except thrushes. The tags weigh less than 3% of the birds’ mass, which is considered an ethical standard in this field. The tags we will use are commonplace in bird migration research, have been used in hundreds of studies (Bridge et al. 2013; McKinnon et al. 2018), and have been shown to not have an impact survival rates (Peterson et al. 2015; Brlík et al. 2020). My advisor has already obtained IACUC approval for the project and has applied for the appropriate banding permits from the federal and state government.
Birds will be captured through target netting using mist nets. Most work will take place off UMBS property on nearby State and National Forest land (with appropriate permits) in the northern Lower Peninsula and eastern Upper Peninsula. However, we are hoping to use UMBS as a home base, and so we also seek permission to work on UMBS property. Specifically, we propose to attach tags to individuals of several of these species that breed commonly on UMBS property, including Red-eyed Vireo, Hermit Thrush, Veery, Yellow-rumped Warbler, and White-throated Sparrow. Capturing and releasing these species will not require any equipment installed on the property or other modifications to the land, as we will be “target-netting”. This approach involves two people holding up a mistnet while attracting the bird with an audio lure, rather than installing a mist-net lane. Owing to the dispersed nature of bird territories, we will have to do some exploring to identify the specific locations where territories are found, but we are happy to coordinate with other researchers to make sure we are not working in any sensitive areas that would be disturbed by our temporary presence.
This project will entail three field seasons—in summers 2023-2025. The field work will take place from the last week of May to the first week of July, in order to maximize male territoriality while ensuring the captured birds are on their breeding grounds and not their migratory pathways. In summer 2023, we affixed 88 tags to seven songbird species -- each of the above species except for Yellow-rumped Warbler, along with V. solitarius (Blue-headed Vireo), which was removed from the summer 2024 target list due to field challenges in capturing this canopy-dwelling species. This summer, we must recover and extract the data from these previously-tagged birds (the tags do not contain a transmitter, so the birds must be recaptured). Estimates of recapture rates for birds tagged on their breeding territories range from 30-50%. We will affix additional tags in 2024 for recovery in summer 2025.
We will download and analyze the archival data directly following the summer 2024 field season, use several existing R packages to estimate locations from light and pressure data, and perform comparative analyses.