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El Niño-Southern Oscillation is linked to decreased energetic condition in long-distance migrants.

Paxton KL, Cohen EB, Paxton EH, Németh Z, Moore FR - PLoS ONE (2014)

Bottom Line: Predicting how migratory animals respond to changing climatic conditions requires knowledge of how climatic events affect each phase of the annual cycle and how those effects carry-over to subsequent phases.In contrast, NDVI values did not differ between El Niño and La Niña years in Caribbean-Central America, and we found no difference in energetic condition or use of coastal habitats for migrants en route from Caribbean-Central America wintering areas.Increased frequency and intensity of ENSO events over the coming decades, as predicted by climatic models, may disproportionately influence long-distance migrants over-wintering in South America.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, The University of Southern Mississippi, Hattiesburg, Mississippi, United States of America.

ABSTRACT
Predicting how migratory animals respond to changing climatic conditions requires knowledge of how climatic events affect each phase of the annual cycle and how those effects carry-over to subsequent phases. We utilized a 17-year migration dataset to examine how El Niño-Southern Oscillation climatic events in geographically different regions of the Western hemisphere carry-over to impact the stopover biology of several intercontinental migratory bird species. We found that migratory birds that over-wintered in South America experienced significantly drier environments during El Niño years, as reflected by reduced Normalized Difference Vegetation Index (NDVI) values, and arrived at stopover sites in reduced energetic condition during spring migration. During El Niño years migrants were also more likely to stopover immediately along the northern Gulf coast of the southeastern U.S. after crossing the Gulf of Mexico in small suboptimal forest patches where food resources are lower and migrant density often greater than larger more contiguous forests further inland. In contrast, NDVI values did not differ between El Niño and La Niña years in Caribbean-Central America, and we found no difference in energetic condition or use of coastal habitats for migrants en route from Caribbean-Central America wintering areas. Birds over-wintering in both regions had consistent median arrival dates along the northern Gulf coast, suggesting that there is a strong drive for birds to maintain their time program regardless of their overall condition. We provide strong evidence that not only is the stopover biology of migratory landbirds influenced by events during the previous phase of their life-cycle, but where migratory birds over-winter determines how vulnerable they are to global climatic cycles. Increased frequency and intensity of ENSO events over the coming decades, as predicted by climatic models, may disproportionately influence long-distance migrants over-wintering in South America.

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Capture rate and ENSO events.Comparison of average capture rate of stopover migrant species that over-wintered in (A) South and (B) Caribbean-Central America during El Niño, La Niña, and non-ENSO years. Error bars represent ± SE and dashed lines represent average values for each region (South America: El Niño:  = 1.44±0.29, La Niña:  = 0.81±0.14, non-ENSO:  = 0.97±0.19; Caribbean-Central America: El Niño:  = 1.64±0.30, La Niña:  = 1.29±0.17, non-ENSO:  = 1.08±0.13). There were significant differences between El Niño and La Niña years in the average capture rate for species over-wintering in South America, and average capture rate during non-ENSO years were consistent with La Nina years. Capture rates did not differ between El Niño and La Niña years for species over-wintering in Caribbean-Central America region. However, there was a significant difference in capture rates between non-ENSO and El Niño years, primarily driven by an outlier (2010 Indigo Bunting capture rate). The pattern was no longer significant when the outlier was removed (Caribbean-Central America: El Niño:  = 1.37±0.13 with outlier removed).
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pone-0095383-g003: Capture rate and ENSO events.Comparison of average capture rate of stopover migrant species that over-wintered in (A) South and (B) Caribbean-Central America during El Niño, La Niña, and non-ENSO years. Error bars represent ± SE and dashed lines represent average values for each region (South America: El Niño:  = 1.44±0.29, La Niña:  = 0.81±0.14, non-ENSO:  = 0.97±0.19; Caribbean-Central America: El Niño:  = 1.64±0.30, La Niña:  = 1.29±0.17, non-ENSO:  = 1.08±0.13). There were significant differences between El Niño and La Niña years in the average capture rate for species over-wintering in South America, and average capture rate during non-ENSO years were consistent with La Nina years. Capture rates did not differ between El Niño and La Niña years for species over-wintering in Caribbean-Central America region. However, there was a significant difference in capture rates between non-ENSO and El Niño years, primarily driven by an outlier (2010 Indigo Bunting capture rate). The pattern was no longer significant when the outlier was removed (Caribbean-Central America: El Niño:  = 1.37±0.13 with outlier removed).

Mentions: Consistent with our prediction we found that in El Niño years focal species over-wintering in South America had reduced energetic conditions (Fig. 2a, Table 2; n = 48, F = 4.22, p = 0.02) and consistently higher capture rates at the stopover site (Fig. 3a, Table 2; n = 51, F = 2.71, p = 0.06) compared to La Niña and non-ENSO years. Energetic conditions and rates of capture during non-ENSO years were similar to La Niña years (Fig. 2a & 3a, Table 2). During El Niño years, energetic condition of birds en route from South America was almost half the value of birds captured during La Niña years (El Niño:  = 1.52±0.29, La Niña:  = 2.49±0.32), with twice as many birds utilizing the coastal stopover site (El Niño:  = 1.54±0.29, La Niña:  = 0.81±0.14). Contrary to our prediction, reduced energetic condition during El Niño years did not result in a later median arrival date for focal species over-wintering in South America at the stopover site compared to La Niña and non-ENSO years; however, birds arrived earlier during non-ENSO years (Fig. 4a, Table 2; n = 51, F = 3.15, p = 0.05).


El Niño-Southern Oscillation is linked to decreased energetic condition in long-distance migrants.

Paxton KL, Cohen EB, Paxton EH, Németh Z, Moore FR - PLoS ONE (2014)

Capture rate and ENSO events.Comparison of average capture rate of stopover migrant species that over-wintered in (A) South and (B) Caribbean-Central America during El Niño, La Niña, and non-ENSO years. Error bars represent ± SE and dashed lines represent average values for each region (South America: El Niño:  = 1.44±0.29, La Niña:  = 0.81±0.14, non-ENSO:  = 0.97±0.19; Caribbean-Central America: El Niño:  = 1.64±0.30, La Niña:  = 1.29±0.17, non-ENSO:  = 1.08±0.13). There were significant differences between El Niño and La Niña years in the average capture rate for species over-wintering in South America, and average capture rate during non-ENSO years were consistent with La Nina years. Capture rates did not differ between El Niño and La Niña years for species over-wintering in Caribbean-Central America region. However, there was a significant difference in capture rates between non-ENSO and El Niño years, primarily driven by an outlier (2010 Indigo Bunting capture rate). The pattern was no longer significant when the outlier was removed (Caribbean-Central America: El Niño:  = 1.37±0.13 with outlier removed).
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4008376&req=5

pone-0095383-g003: Capture rate and ENSO events.Comparison of average capture rate of stopover migrant species that over-wintered in (A) South and (B) Caribbean-Central America during El Niño, La Niña, and non-ENSO years. Error bars represent ± SE and dashed lines represent average values for each region (South America: El Niño:  = 1.44±0.29, La Niña:  = 0.81±0.14, non-ENSO:  = 0.97±0.19; Caribbean-Central America: El Niño:  = 1.64±0.30, La Niña:  = 1.29±0.17, non-ENSO:  = 1.08±0.13). There were significant differences between El Niño and La Niña years in the average capture rate for species over-wintering in South America, and average capture rate during non-ENSO years were consistent with La Nina years. Capture rates did not differ between El Niño and La Niña years for species over-wintering in Caribbean-Central America region. However, there was a significant difference in capture rates between non-ENSO and El Niño years, primarily driven by an outlier (2010 Indigo Bunting capture rate). The pattern was no longer significant when the outlier was removed (Caribbean-Central America: El Niño:  = 1.37±0.13 with outlier removed).
Mentions: Consistent with our prediction we found that in El Niño years focal species over-wintering in South America had reduced energetic conditions (Fig. 2a, Table 2; n = 48, F = 4.22, p = 0.02) and consistently higher capture rates at the stopover site (Fig. 3a, Table 2; n = 51, F = 2.71, p = 0.06) compared to La Niña and non-ENSO years. Energetic conditions and rates of capture during non-ENSO years were similar to La Niña years (Fig. 2a & 3a, Table 2). During El Niño years, energetic condition of birds en route from South America was almost half the value of birds captured during La Niña years (El Niño:  = 1.52±0.29, La Niña:  = 2.49±0.32), with twice as many birds utilizing the coastal stopover site (El Niño:  = 1.54±0.29, La Niña:  = 0.81±0.14). Contrary to our prediction, reduced energetic condition during El Niño years did not result in a later median arrival date for focal species over-wintering in South America at the stopover site compared to La Niña and non-ENSO years; however, birds arrived earlier during non-ENSO years (Fig. 4a, Table 2; n = 51, F = 3.15, p = 0.05).

Bottom Line: Predicting how migratory animals respond to changing climatic conditions requires knowledge of how climatic events affect each phase of the annual cycle and how those effects carry-over to subsequent phases.In contrast, NDVI values did not differ between El Niño and La Niña years in Caribbean-Central America, and we found no difference in energetic condition or use of coastal habitats for migrants en route from Caribbean-Central America wintering areas.Increased frequency and intensity of ENSO events over the coming decades, as predicted by climatic models, may disproportionately influence long-distance migrants over-wintering in South America.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, The University of Southern Mississippi, Hattiesburg, Mississippi, United States of America.

ABSTRACT
Predicting how migratory animals respond to changing climatic conditions requires knowledge of how climatic events affect each phase of the annual cycle and how those effects carry-over to subsequent phases. We utilized a 17-year migration dataset to examine how El Niño-Southern Oscillation climatic events in geographically different regions of the Western hemisphere carry-over to impact the stopover biology of several intercontinental migratory bird species. We found that migratory birds that over-wintered in South America experienced significantly drier environments during El Niño years, as reflected by reduced Normalized Difference Vegetation Index (NDVI) values, and arrived at stopover sites in reduced energetic condition during spring migration. During El Niño years migrants were also more likely to stopover immediately along the northern Gulf coast of the southeastern U.S. after crossing the Gulf of Mexico in small suboptimal forest patches where food resources are lower and migrant density often greater than larger more contiguous forests further inland. In contrast, NDVI values did not differ between El Niño and La Niña years in Caribbean-Central America, and we found no difference in energetic condition or use of coastal habitats for migrants en route from Caribbean-Central America wintering areas. Birds over-wintering in both regions had consistent median arrival dates along the northern Gulf coast, suggesting that there is a strong drive for birds to maintain their time program regardless of their overall condition. We provide strong evidence that not only is the stopover biology of migratory landbirds influenced by events during the previous phase of their life-cycle, but where migratory birds over-winter determines how vulnerable they are to global climatic cycles. Increased frequency and intensity of ENSO events over the coming decades, as predicted by climatic models, may disproportionately influence long-distance migrants over-wintering in South America.

Show MeSH
Related in: MedlinePlus