Fitness for birds in warming Alaska

Alaska North Slope looking for eggs
Looking for nests / FrontierScientists footage

Jonathan Perez stands in a remote part of Alaska’s North Slope while White-Crowned Sparrows sing from surrounding shrubs and a Jaeger flies overhead, calling. Perez is listening to the bird calls, recording what species sound out and how many individuals are singing. Next to him, an automated device is attempting to do the same.

Listening to bird populations

“We have these acoustic corridors at our four sites that do four recordings a day for 30 minutes that pick up bird song.” “You put the device out; it’s run off a solar panel, you can leave it all season. You have to go out occasionally and exchange out the cards because the memory fills up but you can visit it weekly and it’s fine.” “One of our jobs is going out and doing validations for these towers because this really hasn’t been used before. So, having birders who know the song, we go out and we stand by the towers while they’re recording and we write down everything we hear.” “If the software comes back and says it hasn’t heard a single White-Crowned Sparrow, [while] we’ve said we’ve heard 15 singing in the area, then something is wrong.” ~Jonathan Perez

After refining software further, the hope is to use the towers as a proxy survey tool to collect and analyze recordings in remote places.

Jonathan Perez and Jesse Krause are graduate student at the University of California Davis in the department of Neural Biology, Physiology and Behavior. They’re working in Alaska on John Wingfield’s lab project: the Birds and Seasonality project, investigating how global climate change is impacting seasonal conditions and resource availability in the Arctic.

Lapland Longspur nest eggs
Lapland Longspur eggs / FrontierScientists footage

Heating up Alaska

Rising temperatures are changing the timing of important life cycle events for migratory songbirds, and the vital plant and insect communities they rely on.

Globally, the temperature increase that occurred between 1900 and 2000 was the largest for any century during the last 1000 years. Over the last six decades, Alaska has warmed twice as fast as the rest of the United States. Average annual Alaska air temperatures increased 3 degrees Fahrenheit during that time, while average winter Alaska air temperatures have increased by 6 degrees Fahrenheit.

Alaska is changing and trends are expected to continue: average annual Alaska air temperatures are forecast to increase another 2 to 4 degrees Fahrenheit by 2050.


Warming temperatures in Alaska’s North Slope are driving shrub cover expansion; shrubs are beating out other tundra plants like mosses and lichen. That means more favorable nesting grounds for shrub breeding birds like White-Crowned Sparrows and less favorable habitat for open tundra breeding birds like the Lapland Longspur.

Members of the Birds and Seasonality project (Team Bird) investigate bird nests to quantify reproductive success for each species.

“One of the cool things that we’ve noticed – and it’s too early to say for sure if this indeed is a range expansion, but – White Crowns are a newcomer to the Arctic; they have not been a regular breeder like the Lapland which is another interesting distinction between the two. Laplands are Arctic specialists, White Crowns are not. Anecdotally, particularly what John Wingfield has been seeing is that White Crown numbers have increased just over the last 20 years here around Toolik.” ~Jonathan Perez

The expanding shrub habitat provides new opportunities for shrub breeding birds, while potentially restricting opportunities for the birds which used to rule the North Slope spring tundra.

Expanding the range

“They did a pretty detailed bird survey I think in the early 2000’s and birds were, White Crowns, I think the furthest North they found them was basically around Happy Valley which is 334, milepost 334 on the Dalton Highway. There had been 2 singing males there at the time. And admittedly the survey was done along the Haul Road so it’s hard to say what’s off that corridor that isn’t easily accessible from the road, but within that range White Crowns were at 334. These past 2 years, I want to say in 2011, they were doing another survey up the road and they actually found White Crowns singing at milepost 386. And so we’ve been tracking this Northern population, which now, last year we did another survey and found two birds up at 396 we’re pretty sure were not there before because we made a decent effort to survey that far. It was by no means exhaustive. But they were definitely there that next year.” “if the shrubs get all the way [north] to Deadhorse and expand there could possibly be White Crowns up there in the future.” ~Jonathan Perez

“So we’ve been doing a lot of work on the stress physiology of these Northern individuals trying to figure out what is unique about them. Why are they the ones that are there?” ~Jonathan Perez

The team has taken stress physiology samples which show individuals on the leading edge of a range expansion (like the northward moving White-Crowned Sparrows) often have increased stress responses.

“They do tend to have a higher stress response on the Northern limit of a populations range. We’ve seen this in other populations as well, like Lapland Longspurs breeding in Greenland tend to have a higher stress response than [those] breeding here in Alaska. Part of that too could be harsher climates or the habitat isn’t as good, there’s a lot of factors that could contribute.” “The further North you get, you know, you have reductions in habitat quality which means less food available, less shelter that’s available.” “We always kind of think that this hyper stress response that you see may allow these birds to respond to predation in their environment more rapidly which would promote fitness in those individuals, or survival.” ~Jesse Krause

Scientifically this is still only a story – there is exhaustive testing to be done before results are published. But it makes sense. Conditions and alterations in a habitat or an ecosystem have resounding effects on the organisms involved. If fitness describes a species’ ability to survive and reproduce in its environment, and organisms have evolved through natural selection to maximize fitness and thrive in certain environmental conditions, then the changing regime of modern-day climate poses a challenge.

Lapland Longspur nest building
Lapland Longspur female with Ptarmigan feather to use in nest building / FrontierScientists footage


Plants and animals experience life cycle events which are likely to occur at a certain time of year. Plants bud and flower. Birds breed, lay eggs, and raise clutches of chicks. Phenology is the study of biological events – it asks when these life cycle events occur, and why.

Phenological events, though, are not necessarily written in stone. Plant phenology, which is tied to environmental conditions, may change as the environment does. Most Arctic plants bud and flower on a schedule governed majorly by when the snow melts and in part by nutrient availability. An earlier snow melt foretells an earlier green-up. Meanwhile, animal phenology – governed largely by hormones – meets with more myriad variables.

A study published in the journal Polar Biology titled ‘Phenological advancement in arctic bird species: relative importance of snow melt and ecological factors’ has found phenological advancement in bird species on Alaska’s North Slope; birds there are nesting and laying their eggs earlier. Among Semipalmated Sandpipers, Pectoral Sandpipers, Red-Necked Phalaropes, Red Phalaropes and Lapland Longspurs, the study found that over a period of 9 years the birds prepared nests and laid eggs (or ‘initiated clutches’) 0.4 to 0.8 days earlier every year. The timing of snow melt was found to be the greatest factor encouraging earlier clutch initiation dates, while the timing of plant emergence and growth (‘green-up’) was a less important explanatory factor. From the study:

“Our results suggest some arctic-breeding shorebird and passerine species are altering their breeding phenology to initiate nesting earlier enabling them to, at least temporarily, avoid the negative consequences of a trophic mismatch.” ~J. R. Liebezeit, K. E. B. Gurney, M. Budde, S. Zack, D. Ward

Striving to synchronize

What the birds are instinctively striving to do is to synchronize their clutches of chicks with the height of food abundance. For White-Crowned Sparrows that means insects; the songbirds make up to 30 trips per hour to the nest to feed their offspring a diet heavy in protein-rich arthropods. Chicks and parents alike need to become strong enough to fly back to more southerly breeding grounds at the end of the season. The timing of local snow melt triggers plant growth, insects feed on plants, birds feed on insects. But it’s a relatively narrow window. If migratory bird species miss that window, they are less likely to successfully raise young; lowered reproductive success reduces the species’ fitness.

“Their migration is triggered for the most part by an increase in day length or photo period. So there is no way for them to adjust their departure date. Earlier in the season there are other cues that basically fine tune their departure, such as social cues and local weather cues and some things like this. But photo period is the major driver for activating the axis that can control both reproduction and migration. So if spring does come earlier there is a potential mismatch between resources that are available and when the birds need to utilize those resources to feed their offspring.” ~Jesse Krause

As temperatures and environmental conditions change expansively and rapidly, we are seeing some plants and animals shift along with their favored conditions – in the Northern Hemisphere typically that motion is northward toward the North Pole, or upward toward higher elevations. We wonder whether the flexibility displayed by examples like earlier nesting dates and northward range expansions will preserve species’ fitness as temperatures continue to rise.

Laura Nielsen

Frontier Scientists: presenting scientific discovery in the Arctic and beyond

Migration project


  • FrontierScientists interviews with the quoted scientists during their 2013 research season at Toolik Field Station
  • ‘Effects of climate change on avian life history and fitness‘ Nicole A. Schneider, essay, Sveriges Lantbruks Universitet (2008)
  • ‘North Slope birds nesting earlier to keep pace with earlier snowmelt, study says’ Yereth Rosen, Alaska Dispatch (Jun 28 2014)
  • {*} ‘Phenological advancement in arctic bird species: relative importance of snow melt and ecological factors’ J. R. Liebezeit, K. E. B. Gurney, M. Budde, S. Zack, D. Ward, Polar Biology (May 2014)
  • ‘Region: Alaska’ Third National Climate Assessment (May 2014)
  • {*} ‘Travelling through a warming world: climate change and migratory species’ Robert A. Robinson, Endangered Species Research, doi: 10.3354/esr00095 (Jun 17 2008)