The Critical Connections Program- Studying Denali's Migratory Birds

By Laura Phillips (last updated April, 2016)
a group of researchers hold a small bird that they are working on tagging

NPS Photo

The Critical Connections Program is an effort to expand our knowledge about the year-round needs of the migratory wildlife of Alaska’s National Parklands. It is also used to provide park managers and others with essential information for implementing conservation strategies for these migratory species. The first stage of the program focuses on studying the year-round movements of migratory birds that nest in Denali and building the Alaska National Parklands Migratory Bird Atlas. The Migratory Bird Atlas is an online reference tool that will contain all available information about the migration routes, stopover areas, wintering areas, and conservation issues of migratory birds nesting in Denali.

a small bird is held in a hand

Photo by George Gress

2015-2016 Update

Goals of the program in 2016 include:

  1. Recapture thrushes tagged with geolocators in 2015.
  2. Deploy additional geolocators on selected study species.
  3. Develop proposals for future program funding.
  4. Outline the next migratory species and parks in Alaska to include in the program.
  5. Develop ideas for complimentary research such as breeding success, diet analyses through stable isotopes, and contaminant loads.
  6. Continue to develop education and outreach efforts.

Field Plans

The team will capture and tag birds with light-level geolocators. These geolocators will help identify migration routes, stopover areas, wintering grounds, describe migratory behavior, and start to assess how environmental conditions in these areas relate to survival and reproductive success. Geolocators are data-loggers that record light levels in relation to time. This information can allow researchers to calculate an estimate of the location of a tagged individual. Researchers must recapture tagged birds when they return the next summer to download data collected by geolocators.

Researchers will capture individual birds on their breeding territories using mist nets, decoys, and song playbacks. Once a bird is captured, researchers will remove the geolocator from already tagged individuals or if a new capture, attach a geolocator to the bird. Geolocators area attached using a harness that loops around the bird’s legs allowing the transmitter to rest on its lower back. This design has been successfully used on small birds in other areas of the US. We will also mark each bird with an individual series of color bands. The color bands will help us identify tagged birds that will need recapturing in subsequent summers.

Little is known about the year-round movements of most of Denali’s bird species. In 2015, We chose to begin the Critical Connections Program by studying the three Catharus thrush species (Hermit, Swainson’s and Grey-cheeked). This decision was made because our study will tie into and amplify work being done farther south with Swainson's and Hermit Thrushes. All three species are of conservation concern in at least parts of their range and there is evidence that their distributions are changing in relation to large-scale change in vegetation in Denali. We deployed 19 geolocators on Swainson’s Thrush and 12 on Grey-cheeked Thrush in summer 2015. In 2016, we will re-trap Grey-cheeked and Swainson’s Thrushes to remove those geolocators deployed in 2015. We will also tag additional Grey-cheeked Thrushes to increase our sample size and capture and tag Hermit Thrushes. Other studies have reported recapture rates of 30-40% for Swainson’s Thrushes tagged with geolocators, and we are hoping for a similar rate of recapture for our study.

New target species for capture and tagging in 2016 include a suite of birds that breed in tall shrub habitats along the Denali Park Road. These species include Wilson’s Warbler, Arctic Warbler, Blackpoll Warbler, Orange-crowned Warbler, Golden-crowned Sparrow, and Fox Sparrow. Shrub habitats in the park appear to be expanding with climate change. However, monitoring data suggest bird species nesting in similar habitats may be responding differently to this changing landscape. For example, the abundance of Wilson’s Warblers appears to be declining by 4% annually while Fox Sparrows are increasing at over 6% annually. Data also suggests some species such as Hermit Thrush and Blackpoll Warbler are increasing their occupancy of shrub habitats in the park while others such as Artic Warblers are exhibiting a decline in occupancy. Understanding the drivers of these changes in density and distribution of bird species requires managers have information on their full annual cycle.

Primary fieldwork will be conducted in Denali from 25 May – 4 June. Field efforts will continue through July as a need to recover and deploy tags.

This project is made possible with support from the National Park Service, Alaska Geographic, Murie Science and Learning Center, and the Denali Education Center.

More Information

Last updated: May 5, 2016