Critical Connections: Studying Migratory Birds

Media Included

  1. Studying Migratory Birds: The Critical Connections Project - In 2015, researchers began a multi-year project to track and study migratory birds that spend their summer in Denali and their winter in points throughout the tropics. This first video explores why studying migratory birds is so important, and how it's such a difficult endeavor compared to studying Denali's year-round residents.
  2. Using Geo-locators to Study Migratory Birds - In this short video, naturalists Scott Weidensaul and Iain Steinhouse describe how tiny backpack-like geo-locaters are used to study small birds, like gray-cheeked and Swainson's thrushes.

Many national parks exist to protect wildlife - but how do you protect animals like migratory birds that leave a park for six months or more? First, you must understand where they go.

In 2015, as part of a multi-year project, a research crew visited nesting territories along the Denali Park Road to capture and tag thrushes with lightweight geolocators.

These are very small data-loggers that will allow us to identify migration routes, stopover areas, and wintering grounds of tagged birds.

How Small Birds Tell a Big Story

Conserving migratory species is one of the greatest challenges facing the National Park Service, particularly as human activities spread across areas used by migratory animals.

Migratory birds that nest in parks present unique conservation challenges because they are influenced by conditions and events in more than one part of the world, including in wintering areas that are often thousands of miles away from their protected breeding grounds.

With support from the National Park Service, Alaska Geographic and the Denali Education Center, we are launching the Critical Connections Program to expand our knowledge about the year-round needs of the migratory wildlife of Alaska’s National Parklands and to provide park managers and others with information essential for implementing effective conservation strategies for these migratory species.

The first stage (2015) of the program focused on:

  • following the year-round movements of migratory birds that nest in Denali and seeing how conditions across their year-round range affect their ability to return to northern breeding grounds and successfully produce young; and

  • building the Alaska National Parklands Migratory Bird Atlas, 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 Alaska’s National Parklands

In future years, the study aims to recapture as many of the 2015 birds as possible. Doing so will let us recover the data collected during each bird's time away from Alaska. This location data will let scientists pin-point the journey each individual bird made, providing insights on the kinds of challenges each face during their seasonal migrations, as well as in their winter range.

Why Study Migratory Birds?

National parks carry different meanings for people. Some love the solitude that a wilderness environment like Denali can offer. Others appreciate a landscape only lightly touched by the hand of humans, while many who visit parks are keen to see wildlife in their natural habitat.

Birds of all kinds are a piece of what makes a place like Denali so valuable to society. Without birds, animal lovers have fewer creatures to view. Without birds, the soundscape of the natural world grows quieter. Without birds, a given ecosystem could change dramatically.

But parks can't protect migratory birds entirely, since they leave each year and often fly thousands of miles away to entirely different countries. In order to understand how to protect birds breeding in a park like Denali, we need to understand where else they live during the year, and what battles they face in those places, such as habitat loss, predation or competition.

Discovering the details of migratory birds is therefore the focus of the Critical Connections project.


How Do You Study Such Small Birds?

a small grayish bird with a tiny backpack on, being held in a person's hand
A thrush sporting its backpack-like data logger, about to be released after capture.

NPS Photo / Nina Chambers

Small migratory birds like thrushes spend a few short months in Alaska. During those summer months, the sun rises around 3 AM and sets after midnight; and since birds are often most active around sunrise, this means bird researchers must set off into the field super early!


The first step is to capture the birds, using mist nets. The nets must be set up in areas where particular birds are likely to live -- so in the case of gray-cheeked thrushes, the research team set up nets along creeks in Denali where plenty of willow bushes grow. Swainson's thrushes, meanwhile, are more likely found in mixed or spruce-dominated forests.

Measuring, Banding and Attaching Geolocators

After a bird is captured, researchers carefully record data about that individual. Measurements are taken of the wing and tail features, and their overall condition is noted.

A unique band is attached to one leg, which indicates the gender of the bird and is also used to identify a specific individual. This is critical, so that the path of each unique bird can be determined, if they are recaptured in successive years.

man taking a photo of a bird that a woman is holding
A band is placed on the bird's leg to help identify it in future years of the study. Measurements and photos are taken of its wings, to help understand the health and condition of each individual. The birds are then carefully fitted with their geolocator backpacks and set free.

NPS Photo


The Geolocators

The backpacks given to each bird monitor and log light levels. Using the time of sunrise and sunset, researchers can estimate the location of a bird to within a few dozen miles.

The devices do not transmit their data in any way. Instead, researchers must return in future years to the initial capture location and retrieve the geolocators. This means 2015 data will not become available until the next year, at the earliest.

Why Track Individuals?

Scientists can put two dots on a map for most bird species. They know that certain birds breed in one place, like Denali National Park, and spend the winter in another place, like Colombia or Venezuela. Not much else is known about their lives, however, including their specific flyways, or migration routes.

The Critical Connections project aims to connect those two dots. Once researchers know the path of a given bird, they can begin to understand the specific challenges that bird might face on its way between summer breeding grounds and where they winter. Knowing this, we can begin to understand what, if any, actions humans can take to help these tiny creatures survive the thousands of miles they journey each year.


This project is only possible through support from a variety of non-government partners, including:


This study also couldn't happen without the hard work of many individuals, who woke up at 2:00 am to help capture and tag birds, helped plan meals for the field crew, or offered decades of expertise in biology. Many thanks to:

  • Jill Boelsma, DEC
  • Iain Stenhouse, BRI
  • Scott Weidensaul
  • George Gress
  • Jason Reppert
  • Laura Phillips
  • Carol McIntyre

Last updated: April 20, 2016