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A Continent-Wide Migratory Divide in North American Breeding Barn Swallows (Hirundo rustica).

Hobson KA, Kardynal KJ, Van Wilgenburg SL, Albrecht G, Salvadori A, Cadman MD, Liechti F, Fox JW - PLoS ONE (2015)

Bottom Line: We identified an east-west continental migratory divide for barn swallows with birds from western regions (Washington State, USA (n = 8) and Saskatchewan, Canada (n = 5)) traveling shorter distances to wintering areas ranging from Oregon to northern Colombia than eastern populations (Ontario (n = 3) and New Brunswick (n = 10), Canada) which wintered in South America south of the Amazon basin.A single swallow from a stable population in Alabama shared a similar migration route to eastern barn swallows but wintered farther north in northeast Brazil indicating a potential leap frog pattern migratory among eastern birds.Six of 9 (67%) birds from the two eastern populations and Alabama underwent a loop migration west of fall migration routes including around the Gulf of Mexico travelling a mean of 2,224 km and 722 km longer on spring migration, respectively.

View Article: PubMed Central - PubMed

Affiliation: Science and Technology Branch, Environment Canada, Saskatoon, Saskatchewan, Canada.

ABSTRACT
Populations of most North American aerial insectivores have undergone steep population declines over the past 40 years but the relative importance of factors operating on breeding, wintering, or stopover sites remains unknown. We used archival light-level geolocators to track the phenology, movements and winter locations of barn swallows (Hirdundo rustica; n = 27) from populations across North America to determine their migratory connectivity. We identified an east-west continental migratory divide for barn swallows with birds from western regions (Washington State, USA (n = 8) and Saskatchewan, Canada (n = 5)) traveling shorter distances to wintering areas ranging from Oregon to northern Colombia than eastern populations (Ontario (n = 3) and New Brunswick (n = 10), Canada) which wintered in South America south of the Amazon basin. A single swallow from a stable population in Alabama shared a similar migration route to eastern barn swallows but wintered farther north in northeast Brazil indicating a potential leap frog pattern migratory among eastern birds. Six of 9 (67%) birds from the two eastern populations and Alabama underwent a loop migration west of fall migration routes including around the Gulf of Mexico travelling a mean of 2,224 km and 722 km longer on spring migration, respectively. Longer migration distances, including the requirement to cross the Caribbean Sea and Gulf of Mexico and subsequent shorter sedentary wintering periods, may exacerbate declines for populations breeding in northeastern North America.

No MeSH data available.


Related in: MedlinePlus

Inter-individual distances (km) between wintering sites (from mean wintering location; see Methods) of barn swallows fit with archival light-level geolocators from four populations in North America.The horizontal midlines within the boxes represent the median value, boxes depict the 25th to 75th percentile range of the data, the whiskers extend 1.5 times beyond the interquartile range, black circles indicate outliers and the horizontal blue line denotes the overall mean of inter-individual wintering distances (1,788 km).
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pone.0129340.g002: Inter-individual distances (km) between wintering sites (from mean wintering location; see Methods) of barn swallows fit with archival light-level geolocators from four populations in North America.The horizontal midlines within the boxes represent the median value, boxes depict the 25th to 75th percentile range of the data, the whiskers extend 1.5 times beyond the interquartile range, black circles indicate outliers and the horizontal blue line denotes the overall mean of inter-individual wintering distances (1,788 km).

Mentions: Barn swallows showed low migratory connectivity with birds from Saskatchewan (orthodromic distance; = 948 ± 603 km) wintering closer together than birds from other populations (Figs 1 and 2). Washington State birds had a large north-south gradient in wintering areas, settling an average of 2,093 ± 1,401 km apart. Birds from Ontario and New Brunswick were dispersed across the central part of South America, settling 1,488 ± 663 km and 1,793 ± 867 km apart, respectively. Population was a significant predictor of arrival date to wintering grounds (F3,22 = 9.24, P < 0.001, adjusted r2 = 0.50) but not sex (F1,23 = 1.66, P = 0.21, adjusted r2 = 0.03). Saskatchewan birds ( = November 30 ± 14.0 d) arrived significantly later to the breeding grounds than Ontario ( = October 15 ± 20.8 d) and New Brunswick ( = October 24 ± 14.3) birds but not Seattle ( = November 14 ± 15.7 d) birds. Swallows from Seattle arrived on the wintering grounds significantly later than swallows from New Brunswick. Length of time at the wintering site ( = 151 ± 19 d) was not significant for sex (F1,18 = 2.88, P = 0.11, adjusted r2 = 0.09) or population (F3,16 = 0.74, P = 0.54, adjusted r2 = -0.04).


A Continent-Wide Migratory Divide in North American Breeding Barn Swallows (Hirundo rustica).

Hobson KA, Kardynal KJ, Van Wilgenburg SL, Albrecht G, Salvadori A, Cadman MD, Liechti F, Fox JW - PLoS ONE (2015)

Inter-individual distances (km) between wintering sites (from mean wintering location; see Methods) of barn swallows fit with archival light-level geolocators from four populations in North America.The horizontal midlines within the boxes represent the median value, boxes depict the 25th to 75th percentile range of the data, the whiskers extend 1.5 times beyond the interquartile range, black circles indicate outliers and the horizontal blue line denotes the overall mean of inter-individual wintering distances (1,788 km).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4466147&req=5

pone.0129340.g002: Inter-individual distances (km) between wintering sites (from mean wintering location; see Methods) of barn swallows fit with archival light-level geolocators from four populations in North America.The horizontal midlines within the boxes represent the median value, boxes depict the 25th to 75th percentile range of the data, the whiskers extend 1.5 times beyond the interquartile range, black circles indicate outliers and the horizontal blue line denotes the overall mean of inter-individual wintering distances (1,788 km).
Mentions: Barn swallows showed low migratory connectivity with birds from Saskatchewan (orthodromic distance; = 948 ± 603 km) wintering closer together than birds from other populations (Figs 1 and 2). Washington State birds had a large north-south gradient in wintering areas, settling an average of 2,093 ± 1,401 km apart. Birds from Ontario and New Brunswick were dispersed across the central part of South America, settling 1,488 ± 663 km and 1,793 ± 867 km apart, respectively. Population was a significant predictor of arrival date to wintering grounds (F3,22 = 9.24, P < 0.001, adjusted r2 = 0.50) but not sex (F1,23 = 1.66, P = 0.21, adjusted r2 = 0.03). Saskatchewan birds ( = November 30 ± 14.0 d) arrived significantly later to the breeding grounds than Ontario ( = October 15 ± 20.8 d) and New Brunswick ( = October 24 ± 14.3) birds but not Seattle ( = November 14 ± 15.7 d) birds. Swallows from Seattle arrived on the wintering grounds significantly later than swallows from New Brunswick. Length of time at the wintering site ( = 151 ± 19 d) was not significant for sex (F1,18 = 2.88, P = 0.11, adjusted r2 = 0.09) or population (F3,16 = 0.74, P = 0.54, adjusted r2 = -0.04).

Bottom Line: We identified an east-west continental migratory divide for barn swallows with birds from western regions (Washington State, USA (n = 8) and Saskatchewan, Canada (n = 5)) traveling shorter distances to wintering areas ranging from Oregon to northern Colombia than eastern populations (Ontario (n = 3) and New Brunswick (n = 10), Canada) which wintered in South America south of the Amazon basin.A single swallow from a stable population in Alabama shared a similar migration route to eastern barn swallows but wintered farther north in northeast Brazil indicating a potential leap frog pattern migratory among eastern birds.Six of 9 (67%) birds from the two eastern populations and Alabama underwent a loop migration west of fall migration routes including around the Gulf of Mexico travelling a mean of 2,224 km and 722 km longer on spring migration, respectively.

View Article: PubMed Central - PubMed

Affiliation: Science and Technology Branch, Environment Canada, Saskatoon, Saskatchewan, Canada.

ABSTRACT
Populations of most North American aerial insectivores have undergone steep population declines over the past 40 years but the relative importance of factors operating on breeding, wintering, or stopover sites remains unknown. We used archival light-level geolocators to track the phenology, movements and winter locations of barn swallows (Hirdundo rustica; n = 27) from populations across North America to determine their migratory connectivity. We identified an east-west continental migratory divide for barn swallows with birds from western regions (Washington State, USA (n = 8) and Saskatchewan, Canada (n = 5)) traveling shorter distances to wintering areas ranging from Oregon to northern Colombia than eastern populations (Ontario (n = 3) and New Brunswick (n = 10), Canada) which wintered in South America south of the Amazon basin. A single swallow from a stable population in Alabama shared a similar migration route to eastern barn swallows but wintered farther north in northeast Brazil indicating a potential leap frog pattern migratory among eastern birds. Six of 9 (67%) birds from the two eastern populations and Alabama underwent a loop migration west of fall migration routes including around the Gulf of Mexico travelling a mean of 2,224 km and 722 km longer on spring migration, respectively. Longer migration distances, including the requirement to cross the Caribbean Sea and Gulf of Mexico and subsequent shorter sedentary wintering periods, may exacerbate declines for populations breeding in northeastern North America.

No MeSH data available.


Related in: MedlinePlus