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Migratory routes and wintering locations of declining inland North American Common Terns | The Auk

For the 3 relative abundance scenarios, the estimated strength of MC with corresponding estimates of sampling error in parentheses was as follows: Median latitude and longitude were quantified on the basis of location estimates occurring between December 15 and March Wintering locations were identified on the basis of estimates from movement models for the 4 lakes. Two years of data were collected from a geolocator retrieved from a bird on one of the Lake Superior colonies Interstate Island in The bird, a male hatched on Interstate Island in , was 9 yr old at the time of deployment The number and location of stopover sites identified were similar for both autumn and spring migration, although timing of migration and length of stopovers varied slightly between years Figure 3 and Supplemental Material Table S6.

For detailed migration schedules, see Supplemental Material Table S6. Date of departure from the breeding lake varied significantly by sex and lake; on average, females departed earlier August 9 than males August 24 and birds from Lake Winnipeg and Oneida Lake departed later August 28 and August 26, respectively than birds from Lake Superior and Lake Huron August 2 and August 15, respectively Table 4. Arrival at wintering grounds also varied by sex, but not by lake or year; on average, females arrived earlier than males November 2 and November 20, respectively Table 4.

Finally, date of arrival at the breeding colony in spring was significantly different between sexes; on average, males arrived 1 wk earlier than females Table 4. Timing and duration of migration, timing of arrival at wintering grounds, median wintering location, and time spent on wintering grounds for male and female Common Terns from 4 North American breeding lakes: Tracking Common Terns throughout their annual cycle allowed us to document important routes, migration schedules, and wintering locations of individuals from the declining North American inland-breeding population.

The nonbreeding distributions identified in our study suggest that Common Terns nesting in southern Manitoba Lake Winnipeg are part of the Central population unit, providing additional insight into where Central and Northwestern population units potentially diverge. We also documented a high degree of intermixing among the inland colonies during the nonbreeding season, with many birds wintering in coastal Peru, a location where large concentrations of waterbirds are known to depend on adequate food and habitat for survival Blokpoel et al.

Some evidence exists for a longitudinal gradient in the use of migration routes and stopover sites among the colonies. Birds from the western breeding colonies lakes Winnipeg and Superior followed a pattern similar to a clockwise loop migration e. By contrast, individuals from Lake Huron used migratory routes that followed a more direct north—south route, and Common Terns from Oneida Lake showed a pattern of counterclockwise loop migration. It is noteworthy that we documented substantial use of inland locations during autumn migration, when it was previously thought that most inland populations of Common Terns migrated from the lower Great Lakes to the U.

Atlantic coast before continuing south Haymes and Blokpoel , Blokpoel et al. Not only did birds appear to be using inland sites, but many remained for several weeks to in a few cases months and didn't stop along the U. Atlantic coast at all. During spring migration, birds used fewer stopover locations and stayed for shorter periods than during autumn migration, which is typical of many migratory birds Horton et al. On average, females departed from the breeding colonies and arrived on the wintering grounds earlier than males; this behavior is consistent with observations by Nisbet et al.

In general, departure dates were more variable than arrival dates, which were likely determined by local postbreeding conditions e. Although we expected females to depart the breeding colony earlier than males, based on observations of Nisbet et al. The observed differences in arrival dates at wintering grounds between males and females suggest that, in general, when females leave the breeding colony they don't extend the postbreeding period elsewhere, leading to earlier female arrival dates.

However, the amount of overlap in arrival date at wintering grounds between sexes could also potentially reflect variation in the extent of male postfledging care or juvenile survival. We didn't observe differences in median wintering locations latitudes between sexes, although this has been observed in Common Terns nesting in the German North Sea, where females wintered farther north than males Becker et al. Adult Common Terns returning to breed in the spring typically look for previous mates, or for a new partner, within a few days of arrival at the breeding colony Ludwig and Becker , Nisbet et al.

In our study, males were estimated to return to the breeding area approximately a week earlier than females, which contradicts reports that males and females arrive at the same time. However, because we buffered each breeding colony by km, to more accurately identify true departure dates, it is possible that earlier-arriving males staged somewhere within the buffered zone without actually returning directly to the breeding colony. Therefore, males and females may still have returned to their respective breeding colonies more synchronously.

Many birds moved throughout the nonbreeding, nonmigratory period, often spending a few weeks to a few months in one location before moving to another.

However, most birds in our study spent the majority of the nonbreeding season along the coast of Peru, which was previously identified as an important wintering location for Great Lakes Common Terns, based on observations of color-banded birds Austin , Blokpoel et al. The high degree of intermixing of birds from each of the 4 inland lakes suggests high population spread and weak connectivity among inland colonies; high intermixing was also proposed recently, based on band encounter data, at least for birds from the Great Lakes region Culp et al.

It is suggested that under weak connectivity, a localized catastrophic event on the wintering grounds would have a diffuse effect across multiple breeding populations Webster and Marra This observation reinforces the need to consider scale when examining levels of migratory connectivity Finch et al. Because there is a high rate of dispersal among Great Lakes breeding colonies Cuthbert et al.

The degree of segregation between inland and Atlantic populations was estimated to be high, based on band re-encounters Cohen et al. Together, these results suggest that at a continental scale, Common Terns breeding in North America show strong connectivity i. Results from our study support the inclusion of the Oneida Lake colony as part of the Central unit, which was previously suggested on the basis of band re-encounter data Cuthbert and Wires , Nisbet et al.

Birds nesting in Lake Winnipeg also appear to be part of the Central unit, based on nonbreeding distributions identified in our study. However, several Common Terns banded in Manitoba, including one from Lake Winnipeg, were recovered on the Pacific coast between Mexico and El Salvador, where Northwest-unit birds are known to winter, which suggests that Manitoba could be the boundary where Northwest and Central populations diverge Nisbet et al.

Increasing banding efforts and using tracking technologies to identify the migration routes and wintering areas used by Common Terns breeding in the Northwest unit i. Lawrence River and Quebec is an important next step in determining where migratory patterns diverge at the edges of the 3 broadly defined population units. Although little is known about winter site fidelity of Common Terns, evidence from banding records reported by Nisbet et al. Common Terns from the Great Lakes region, including birds from our study, have been observed in coastal Peru during consecutive years, based on mark—resighting data e.

The Common Tern in our study for which we have 2 yr of tracking data used similar migration routes and wintering locations in successive years. Because of the small number of multiyear observations in our study and in previous studies Haymes and Blokpoel , Becker et al. However, based on these collective observations, this species appears to display moderate to high levels of winter site fidelity. This information is important from a conservation perspective, because it will be difficult to determine the effects of localized events or to predict future threats without confirmation that birds are returning to the same wintering sites.

The degree of fidelity is likely associated with changes in food availability, which is directly linked to biotic and abiotic conditions on the wintering grounds Becker et al. A recent genetic study, aimed at identifying the population structure of inland and eastern North American Common Tern colonies, found evidence of asymmetrical dispersal from inland to coastal colonies thought to be associated with nonbreeding distributions Szczys et al. Dispersal rates from inland colonies to the Atlantic coast have increased tenfold since the s, which may partly explain the apparent population decline of inland colonies during this period.

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Although similar management strategies have been implemented at inland and coastal colonies, the Atlantic coast population is considered stable, whereas the Central population continues to decline. Because these populations don't overlap on their wintering grounds, a focus on nonbreeding habitat use and juvenile dispersal will be important for understanding metapopulation dynamics Szczys et al.

Additional genetic analyses of Common Terns breeding in the western portion of the Central unit and Northwest unit, as well as use of stable isotopes, are needed to further identify and quantify dispersal among units. Weak migratory connectivity among the 4 inland lakes and consistent declines in nest numbers throughout the Central unit make it difficult to identify bottlenecks using data loggers alone, because birds must survive and return to the same site for data to be retrieved.

To identify threats, other methods, such as satellite tracking and analysis of mark—recapture data, will be needed to estimate seasonal apparent survival e. Climate change is currently identified as one of the greatest threats to Common Terns worldwide Cabot and Nisbet , Palestis , Nisbet et al. Issues related to climate change—including increased severity of storms, changes in food availability, and rising water levels—are important factors that may negatively affect Common Terns throughout their annual cycle Cuthbert et al.

A recent climate-change vulnerability assessment suggests that migratory distance and degree of habitat specialization during breeding and nonbreeding seasons will likely pose the greatest direct challenges to this species, due to predicted sea-level rise Culp et al. The greatest perceived indirect effect was related to vulnerability of aquatic prey and their habitats in response to climate change Culp et al. Predicted increases in the strength and frequency of storms will be detrimental to Common Terns nesting at inland colonies in North America Cuthbert et al.

At inland breeding colonies, high water levels and severe storm events can erode or inundate island nesting habitats; when these events occur at peak nesting, total nest failure often results Cuthbert et al. Additionally, during years of high water, competition with gulls often increases as a result of reduced availability of nesting habitat Cuthbert et al. Throughout the nonbreeding season, Common Terns follow the distribution and abundance of prey fish Cabot and Nisbet , and the northwest coast of South America is a hot spot for productivity Jahncke et al.

The Peruvian upwelling ecosystem, part of the Humboldt Current System, is one of the most biologically productive marine environments globally Jahncke et al. The cold, nutrient-rich water in this system is important to piscivorous birds that rely on the abundance of pelagic fish for survival Pulido et al. The Peruvian anchovy Engraulis ringens , which is the most abundant pelagic fish in this system, is not only an important species for foraging seabirds but also supports the largest single species fishery on Earth Pulido et al.

Though highly productive, this system is influenced by regional climatic fluctuations that can dramatically alter productivity Jahncke et al. In the late s to early s, the combination of heavy fishing pressure and 2 ENSO events and resulted in the collapse of the anchovy population, which led to major declines in seabird populations Jahncke et al. In addition to pressures from commercial fishing, changes in sea surface temperatures caused by ENSO events further reduced prey availability by altering the distribution and abundance of fish along the Peruvian coast Jahncke et al.

Declines in seabird and shorebird populations have been documented in years of extreme ENSO events such as —, when populations of Red-necked Phalaropes Phalaropus lobatus assumed to be wintering in the region crashed Nisbet and Veit and numbers of Common Terns wintering along the southern coast of Peru were substantially below normal Hughes Although potential impacts of climate change on both breeding productivity and adult survival currently appear to be serious, it is difficult to predict how Common Terns will adapt to future environmental conditions.

Migratory routes and wintering locations of declining inland North American Common Terns | The Auk

Because we have identified Peru as a location where many Common Terns from inland populations concentrate during the nonbreeding season, research on habitat use e. If survival during the nonbreeding season is primarily influenced by environmental factors, such as changing ocean temperatures and fluctuating food supplies, it will be important to better quantify winter site fidelity, monitor where birds are moving, and identify conditions associated with movements.

This knowledge will also reinforce the importance of continued management of inland North American breeding colonies, as well as emphasizing the need for restoration and creation of additional breeding habitats. We thank the many people involved in forming this collaborative effort—most especially I.

Nisbet, for his advice, guidance, and review of the manuscript; and S. Lewis, for his long-term dedication to conservation of Common Terns in the Great Lakes region.

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The Auk: Ornithological Advances and The Condor: Ornithological Studies in Avian Biology is a book series published by the American Ornithology. Society. For Authors | . Among auks, nearly year-round occurrence at breeding colonies has been average annual maximum limit of sea ice indicated with a dashed line. We deployed 5 tags for 13 days in June on a hilltop near the colony as an We then calculated percent volume contours representing 25%, 50%, and.

Hallworth for their assistance to A. We are also thankful for project advice and training from J. Bednar as well as field assistance from R. Minchak; and for logistical support from S. DNA analysis was conducted in part by A. Funding was provided by the U. We acquired all necessary permitting for handling and marking Common Terns in the United States and Canada — Sign Up for E-alerts. Alert me when this article is cited: The pyriform egg of the Common Murre Uria aalge is more stable on sloping surfaces.

Effects of climate change and environmental variability on the carrying capacity of Alaskan seabird populations. Where do winter crows go? Characterizing partial migration of American Crows with satellite telemetry, stable isotopes, and molecular markers.

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Feather growth rate increases with latitude in four species of widespread resident Neotropical birds. Habitat Selection Studies in Avian Ecology: Sign up for e-alerts. Looking for a job? Visit the BioOne Career Center and apply to open positions across the sciences. Log in Admin Help. January 24, ; Published: Field Methods We deployed archival light-level geolocators on Common Terns across the 4 lakes during the breeding seasons of , , and ; the years in which the breeding colonies were visited post-deployment varied by breeding lake Table 1. Analytical Methods The Intigeo and BAS geolocators recorded light readings every minute, with the maximum light recorded every 5 min.

Overall Migration Patterns Flight paths, duration of stay at stopover and wintering locations, and total distance traveled varied among individual birds within and among breeding colonies Figure 1 ; Supplemental Material Table S2 , Table S3 , Figure S1.

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Seasonal differences in landbird migration strategies. Sooty tern Onychoprion fuscatus survival, oil spills, shrimp fisheries, and hurricanes. Trends in carbon flux to seabirds in the Peruvian upwelling system: Effects of wind and fisheries on population regulation. A review of the world's active seabird restoration projects. Journal of Wildlife Management The integration of mark re-encounter and tracking data to quantify migratory connectivity.

Basic data processing for light based geolocation archival tags. The cost of migration: Spoonbills suffer higher mortality during trans-Saharan spring migrations only. Waiting for the mate? Spatial behaviour of Common Terns, Sterna hirundo , during courtship. Post-breeding migration and connectivity of Red Knots in the Western Atlantic.

The Journal of Wildlife Management A call for full annual cycle research in animal ecology. Current status and abundance trends of Common Terns breeding at known coastal and inland nesting regions in Canada. Journal of Great Lakes Research Future coastal population growth and exposure to sea-level rise and coastal flooding—a global assessment.

An explanation for the population crash of Red-necked Phalaropes Phalaropus lobatus staging in the Bay of Fundy in the s. Common Tern Sterna hirundo , version 3. Sexual dimorphism, female—female pairs, and a test for assortative mating in Common Terns. Migrations and winter quarters of five Common Terns tracked using geolocators. Female Common Terns Sterna hirundo start autumn migration earlier than males. There is such a rich diversity of ideas and subjects explored throughout the collection that I think Greengrass is an extremely exciting new author that you should all watch out for.

Let me know your thoughts about our winner or any of the other nominated books! Aloneness makes of us something so much more than we are in the midst of others whose claim is that they know us. The Little Reader Library. The Bookshop Around the Corner. About the Lonesome Reader. Posted December 1, To receive updates when new blog posts appear on Lonesome Reader enter your email address: My Top 10 books of Ghost Wall by Sarah Moss. Normal People by Sally Rooney. Everything Under by Daisy Johnson.

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Migratory routes and wintering locations of declining inland North American Common Terns | The Auk

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