New England is a sea duck's winter wonderland

“Flapping in a winter wonderland”, slightly alter the lyrics to Richard B. Smith’s Winter Wonderland and now we’re talking sea ducks. If you’ve had the pleasure to be on a boat off the shores of New England in the not-so-balmy winter months then you have probably gazed upon rafts comprised of thousands of sea ducks bobbing in the waves. These ducks inhabit our coasts during the winter to take advantage of plentiful food sources while their more northern breeding areas are covered in ice, but just where do these birds go during the rest of the year and what routes do they take to get there? Dustin Meattey, a recently graduated masters student from the University of Rhode Island, partnered with three other wildlife agencies to answer that very question.

White-winged Scoter Movements and Habitat Use in Southern New England, original article published in RI DEM Hunting and Trapping 2018-2019 Regulation Guide

Sea ducks are some of the most prized waterfowl species for duck hunters, wildlife photographers, and birders. The coastal waters and offshore environments in southern New England provide crucial winter habitat for several species including Common Eiders, all three species of scoters (Black, White-winged, Surf), and Long-tailed Ducks. Over the past several decades, population declines of many sea duck species have highlighted the need for a better understanding of their habitat preferences, migration patterns and timing, and linkages between important geographic areas throughout their life cycle. Reasons for these declines remain poorly understood, but habitat conditions and disturbance on the wintering grounds may have carry-over effects impacting annual survival and breeding productivity during subsequent seasons. Because sea ducks spend much of their annual cycle in non-breeding areas where human-induced threats are often greatest, understanding habitat use on their wintering grounds is crucial for conservation planning. As the development of offshore wind power moves closer to large-scale implementation in the northeastern United States, particularly in areas used by sea ducks during winter, identifying important habitats used by wintering sea ducks informs the planning process and helps avoid displacement of sea ducks from preferred habitats.

White-winged Scoter with a satellite transmitter,  Photo credit:  Josh Beuth

White-winged Scoter with a satellite transmitter, Photo credit: Josh Beuth

One species of sea duck that inhabits New England coastal waters during the wintering period is the White-winged Scoter (Melanitta fusca). White-winged Scoters are a long-lived sea duck species that winters along both the Atlantic and Pacific coasts of North America, with increasing numbers also wintering on the Great Lakes. White-winged Scoters nest throughout the interior boreal forest from Alaska to central Canada, with geographically separate eastern and western populations, although some studies have suggested that birds from Atlantic and Pacific coasts may overlap on the breeding grounds. Like most other sea duck species, White-winged Scoters have apparently experienced a long-term population decline throughout the last half-century.

Researchers from Rhode Island Department of Environmental Management (DEM), University of Rhode Island, Biodiversity Research Institute, and the Canadian Wildlife Service partnered together between 2015 and 2018 to study the movement ecology of White-winged Scoters.  We deployed over 50 satellite transmitters in adult females on their wintering grounds in southern New England and at a molting area in the St. Lawrence River Estuary in Quebec. We were able to follow the movements of many individuals for over two years, as they traversed thousands of miles between wintering areas on the East Coast to breeding grounds across the northern boreal forest from Quebec to the Northwest Territories of Canada, on their return migration to important molting and then wintering areas, and for some back again to the breeding grounds.

Fig. 1. Estimated probability of use by adult female White-winged Scoters in nearshore and offshore waters in southern New England based on movements of satellite-tagged birds. For information on the most current wind energy areas, visit  BOEM: Offshore Wind Energy

Fig. 1. Estimated probability of use by adult female White-winged Scoters in nearshore and offshore waters in southern New England based on movements of satellite-tagged birds. For information on the most current wind energy areas, visit BOEM: Offshore Wind Energy

The data gathered from these birds allowed us to calculate the size and habitat characteristics of winter home ranges, and to identify specific areas in southern New England during winter that were preferred by White-winged Scoters (Fig. 1). Our results suggested that offshore sites predicted to be most used by scoters had minimal overlap with currently leased and proposed wind energy areas in southern New England (shown in blue). However, many birds made long-distance flights throughout the winter between areas like Montauk Point, NY and the Nantucket Shoals south of Nantucket Island, therefore they were likely often crossing wind energy areas as they moved between their preferred sites. This suggests that future wind energy development in the currently proposed lease areas could act as a deterrent or barrier to these important within-winter movements.

Using the movement data from these scoters, we were also able to identify and document their primary migration routes between breeding and wintering areas and the timing of these movements (Figs. 2, 3). This information is important for biologists responsible for designating hunting seasons and for protecting key areas used during migration, and for others responsible for managing offshore wind farms and other potential sources of disturbance. White-winged Scoters wintering in coastal New England bred throughout northern Canada from northern Quebec to the Northwest Territories. After leaving the breeding grounds, scoters underwent a month-long wing molt primarily in James Bay and the St. Lawrence River Estuary before continuing their fall migration back to their primary wintering grounds in southern New England. An important finding from this research was that migration timing was consistent among all birds in our study, regardless of where they bred or molted, and regardless of what route they decided to take. Essentially, the eastern portion of the continental White-winged Scoter population seems to function as a single, continuous population with little evidence of any geographically distinct sub-populations. This suggests that our current harvest of White-winged Scoters should not disproportionately target any particular segment of the population.

Our hope is that this project provides helpful information to policy makers, developers, and biologists to best conserve and manage this important species. This study was part of the Atlantic and Great Lakes Sea Duck Migration Study, a multi-partner collaborative project initiated by the Sea Duck Joint Venture.

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About the author:
Dustin Meattey studied Spatial ecology of sea ducks in the Scott McWilliams lab at the University of Rhode Island and is currently a wildlife biologist with Biodiversity Research Institute.

Its fall, so its time to chat about songbird migration in New England!

Migration is a particularly vulnerable time of year for songbirds. Birds are facing novel habitats, exhausting exercise, and are encountering more predators and human modified environments. Why do some bird species take this risk? Birds are in search of predictably abundant resources to eat through the winter, and on their breeding grounds food becomes scarce and highly coveted as temperatures decrease . Birds also spend a large chunk of their annual cycle migrating (see below for a Blackpoll Warbler’s annual cycle to see what I mean). So studying how birds are making these journeys, what they are eating on the way, where they go, when, and in what direction is important and can lead to better decisions about how to help them on their way.

A Blackpoll Warbler’s annual cycle: notice how much time each year it will spend traveling between breeding and wintering locations

A Blackpoll Warbler’s annual cycle: notice how much time each year it will spend traveling between breeding and wintering locations

Understanding how physiological condition (how much fat and/or antioxidant capacity a bird is able to store) influences a bird’s behavior can help us to better understand their needs during this susceptible time. Further, physiological and behavioral actions during spring and fall migration can have consequences that spill over into the winter or breeding seasons (called carry-over effects). We are in the midst of a manipulative field experiment that is trying to tease apart whether fat stores and antioxidant stores are important drivers of decisions birds make during their travels.

But before I start talking just about birds and how cool they are, I want you to take a second and think about an animal that embodies athleticism to you. Did you think of the sprinting cheetah, or the fast swimming sailfish, or maybe the remarkable dive of a hunting peregrine falcon? Well, of course you would be right! All those species are incredibly fast athletes.

However, when I think of any sort of endurance athleticism in the animal world, I tend to think of animals that are migrating – especially migratory birds. Every year thousands of birds make long migrations around the globe, moving from areas of declining resources to areas of abundant resources. And, these birds fly hundreds to thousands of miles in the process, which is a crazy feat of endurance exercise. Among migrating birds, there are definitely some rock stars. The Arctic Tern is pretty famous (to us bird people) since it flies almost 60,000 total miles during migration. As is the Bar-tailed Godwit that migrates nonstop from Alaska to New Zealand or Australia, covering more than 6,000 miles in about 8 days of continuous flying (which is exhausting for me even to contemplate). However, although some birds are able to migrate in one flight, birds have many different strategies to help them travel these enormous distances and there is a lot of variation in how these journeys are made.

First, there could be variation in the routes a bird may take - in North America a songbird breeding in the arctic and wintering in South America may take a completely overland and direct route to get there, or they could fly east and then down the coast and across the gulf or straight across the ocean.

Possible migratory routes birds can take on their way south.

Possible migratory routes birds can take on their way south.

Second, most migrations are not non-stop flights, and therefore, during migration, short periods of endurance flight are traded off with periods of feeding and rest at stopover sites. There may be many stopovers on a bird’s migration from their breeding location their wintering location.

Migration = short endurance flights punctuated with longer periods of rest and refueling with native berries and fruits at stopover sites along the way

Migration = short endurance flights punctuated with longer periods of rest and refueling with native berries and fruits at stopover sites along the way

Migratory stopover sites are crucial for birds to rebuild energy stores, and the time a bird spends on a stopover can influence the timing and success of its overall migration. Additionally, during flight, birds have an elevated metabolism leading to an increase in the production of a byproduct we call reactive species. Reactive species can cause damage to cells, tissues, or DNA if not balanced by antioxidants**. Luckily for the birds, during the fall, there are a ton of seasonally abundant fruits around that are full of dietary antioxidants and fats. Birds that normally eat insects during the rest of the year generally switch to eating these fruits during migratory stopovers. However, the quality of stopover sites and the amount of fruit available to birds varies among sites and across a migratory season. We were curious about whether birds that have more fat and/or antioxidants in their diet can spend less time on a stopover site, and whether they are more likely to depart in a seasonally appropriate (southerly) direction.

To examine these differences, we headed out to Block Island, Rhode Island, an offshore stopover site that is popular for migrating birds and performed a field experiment. We caught four species of birds (Blackpoll Warblers, Hermit Thrushes, Red-Eyed Vireos, and Myrtle Warblers) that varied in their migration patterns, and manipulated their physiological condition.

Looking at multiple species of birds will allow us to compare how important condition is for birds with different migration strategies (land-based vs. over the sea) and migration distances (short vs long). Myrtle Warblers (Setophaga coronata coronata), migrate shorter distances than many of the other species passing through Block Island in the fall, and winter farther north than any other wood warblers. Hermit Thrushes (Catharus guttatus) are medium distance migrants that travel from Block Island to winter in the southern United States and Central America. Red-Eyed Vireos (Vireo olivaceus) are long-distance migrants that regularly stopover on Block Island during the fall. After leaving Block Island they are more likely to migrate overland until they reach the Gulf of Mexico, which means they will probably stop many more times as they travel south. In contrast, after leaving Block Island in the fall, Blackpoll Warblers (Setophaga striata) make an insane journey out across the open ocean for 3-5 days of non-stop flight before reaching a wintering destination in the Caribbean or South America.

We used mist nets to capture these four species and and then kept them in an outdoor aviary for a couple of days to manipulate their physiological condition. Once caught, we either gave the birds a diet rich in fat and/or antioxidants (we called this the ad lib diet) or a diet without extra fat and/or antioxidants (we called this the maintenance diet since birds, well, maintained the weight that we caught them in). We wanted to fatten the birds up (ad lib diet) and give them a lot of dietary antioxidants so that they were in better condition to simulate birds on a stopover site that would be abundant with fruits. We contrasted that diet treatment with the maintenance diet to simulate birds that wouldn’t have as much access to fruits on stopover. We predicted that birds that were able to stuff themselves with fat and antioxidants would be in better condition and would be more likely to migrate sooner and, potentially, reach their wintering grounds sooner than birds that were unable to do so.

We also took blood samples to look at their antioxidant capacity. A bird’s blood can tell us all sorts of levels of circulating antioxidants or other metabolites, kind of like when you go get checked for your cholesterol at the doctor. We predicted that birds given dietary antioxidants would have increase their circulating levels of antioxidants during captivity. After several days in captivity, birds on the fat rich diet had gained a lot of fat, where birds on the maintenance diet were still in the condition that we had caught them in. We then attached small radio-transmitters called Nanotags to these birds. Each nanotag sends out a unique signal every 10 seconds that can be picked up passively by receiving stations in the MOTUS network. We built one of those receiving stations on Block Island, but it was a part of the network of towers that extends from Canada down into South America. If any of our tagged birds fly along the Atlantic flyway then there is a good chance we’ll know about it.

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Automatic Receiving

Station on Block Island

This 40ft tower is a part of the MOTUS network and will passively pick up the signals from any Nanotag within it’s range

Nanotags will help us determine whether birds on an ad lib diet or one that was given dietary antioxidants can leave Block Island sooner and in a more seasonally appropriate direction than those on the maintenance diet or ones not given dietary antioxidants.

Linking behavioral decisions and physiological condition of songbirds together can help us to understand the types of habitats and food resources different bird species need on stopover sites. In turn, that could help to determine how we can best conserve those areas, or how we can restore them by planting native fruits and berries (see this helpful guide on what to plant!) to help these incredible athletes on their way.


**Antioxidant Definition: Animals have a multifaceted antioxidant system made up of endogenous antioxidants, micromolecular sacrificial molecules and dietary antioxidants that work synergistically to protect against oxidative damage (from those pesky reactive species). For birds in migration, the relationship between reactive species production, antioxidant protection and oxidative damage is not straightforward, and various aspects of the antioxidant system may respond differently depending on the type of damage, the duration of flight or the physiological state a bird. Dietary Antioxidants: Antioxidants produced by plants and consumed by animals in their diets. The two broad classes of dietary antioxidants include lipophilic antioxidants (vitamin E or carotenoids) and hydrophilic antioxidants (vitamin C or polyphenols). In this study we specifically examined polyphenols.


 
About the author:   Clara Cooper-Mullin  is a PhD student studying the impacts of diet and body condition on songbird migration the  Scott McWilliams lab  at the University of Rhode Island

About the author:
Clara Cooper-Mullin is a PhD student studying the impacts of diet and body condition on songbird migration the Scott McWilliams lab at the University of Rhode Island

 

Winner of the Big biology category in the ScienceSeeker Awards 2019

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