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Influence of Seasonal Food Availability on the Dynamics of Seabird Feeding Flocks at a Coastal Upwelling Area.

Anguita C, Simeone A - PLoS ONE (2015)

Bottom Line: However, there is scant information on the temporal stability of the composition and abundance of MSFFs as well as the effect of seasonal food availability on their dynamics.Using generalized linear models (GLMs), our results show that the contrasting seasonality in food availability of the study area (using chlorophyll-a concentration as a proxy) had no significant influence on MSFF attributes, sparsely explaining their variations (P>0.05).This would allow them to reduce resource unpredictability, which in turn has a major impact on structuring seabird's MSFF dynamics.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Ecología y Biodiversidad, Facultad de Ecología y Recursos Naturales, Universidad Andrés Bello, Santiago, Chile.

ABSTRACT
The formation of multi-species feeding flocks (MSFFs) through visual recruitment is considered an important strategy for obtaining food in seabirds and its functionality has been ascribed to enhanced foraging efficiency. Its use has been demonstrated in much of the world's oceans and includes numerous species. However, there is scant information on the temporal stability of the composition and abundance of MSFFs as well as the effect of seasonal food availability on their dynamics. Between July 2006 and September 2014, we conducted monthly at-sea seabird counts at Valparaiso Bay (32°56' to 33°01'S, 71°36' to 71°46'W) within the area of influence of the Humboldt Current in central Chile. This area is characterized by a marked seasonality in primary and secondary production associated with upwelling, mainly during austral spring-summer. Based on studies that provide evidence that flocking is most frequent when food is both scarce and patchy, we hypothesized that seabird MSFF attributes (i.e. frequency of occurrence, abundance and composition) will be modified according to the seasonal availability of food. Using generalized linear models (GLMs), our results show that the contrasting seasonality in food availability of the study area (using chlorophyll-a concentration as a proxy) had no significant influence on MSFF attributes, sparsely explaining their variations (P>0.05). Rather than seasonal food availability, the observed pattern for MSFF attributes at Valparaiso Bay suggests a substantial influence of reproductive and migratory (boreal and austral migrants) habits of birds that modulates MSFF dynamics consistently throughout the whole year in this highly variable and patchy environment. We highlight the importance of visual recruitment as a mechanism by which migratory and resident birds interact. This would allow them to reduce resource unpredictability, which in turn has a major impact on structuring seabird's MSFF dynamics.

No MeSH data available.


Box-plot of the seasonal variation in the abundance of each species involved in MSFFs (total number of individuals observed in MSFFs per month) at Valparaiso Bay.Species with frequency of occurrence ≥5% are displayed and sorted from highest to lowest abundance. * indicates species with significant seasonal variation (P<0.05, Table 1).
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pone.0131327.g005: Box-plot of the seasonal variation in the abundance of each species involved in MSFFs (total number of individuals observed in MSFFs per month) at Valparaiso Bay.Species with frequency of occurrence ≥5% are displayed and sorted from highest to lowest abundance. * indicates species with significant seasonal variation (P<0.05, Table 1).

Mentions: Multivariate analysis indicate that MSFF compositional variation (total abundance and presence/absence) is explained mostly by the seasonality (P<0.05; Table 4, Fig 5), with significant differences between all seasons (P<0.05; Table 5). Neither chlorophyll-a concentration nor its interaction with seasonality had a significant multiplicative effect on MSFF composition (P>0.05; Table 4). Species that showed significant seasonal variation are shown in Table 1 and Fig 5. For the vast majority of the abundant species in MSFFs at Valparaiso, there was a negative relation between monthly abundance and chlorophyll-a concentration (univariate analysis; Table 1), indicating that seabirds are engaged in MSFFs with higher abundances in months with lower primary production. However, this trend was significant (P<0.05) only for Southern fulmar, White-chinned petrel, Brown-hooded gull and Westland petrel (for scientific names, see Table 1). As in the multivariate analysis, the interaction of chlorophyll-a concentration and seasonality had no significant effect on any species (P>0.05, Table 1).


Influence of Seasonal Food Availability on the Dynamics of Seabird Feeding Flocks at a Coastal Upwelling Area.

Anguita C, Simeone A - PLoS ONE (2015)

Box-plot of the seasonal variation in the abundance of each species involved in MSFFs (total number of individuals observed in MSFFs per month) at Valparaiso Bay.Species with frequency of occurrence ≥5% are displayed and sorted from highest to lowest abundance. * indicates species with significant seasonal variation (P<0.05, Table 1).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4488391&req=5

pone.0131327.g005: Box-plot of the seasonal variation in the abundance of each species involved in MSFFs (total number of individuals observed in MSFFs per month) at Valparaiso Bay.Species with frequency of occurrence ≥5% are displayed and sorted from highest to lowest abundance. * indicates species with significant seasonal variation (P<0.05, Table 1).
Mentions: Multivariate analysis indicate that MSFF compositional variation (total abundance and presence/absence) is explained mostly by the seasonality (P<0.05; Table 4, Fig 5), with significant differences between all seasons (P<0.05; Table 5). Neither chlorophyll-a concentration nor its interaction with seasonality had a significant multiplicative effect on MSFF composition (P>0.05; Table 4). Species that showed significant seasonal variation are shown in Table 1 and Fig 5. For the vast majority of the abundant species in MSFFs at Valparaiso, there was a negative relation between monthly abundance and chlorophyll-a concentration (univariate analysis; Table 1), indicating that seabirds are engaged in MSFFs with higher abundances in months with lower primary production. However, this trend was significant (P<0.05) only for Southern fulmar, White-chinned petrel, Brown-hooded gull and Westland petrel (for scientific names, see Table 1). As in the multivariate analysis, the interaction of chlorophyll-a concentration and seasonality had no significant effect on any species (P>0.05, Table 1).

Bottom Line: However, there is scant information on the temporal stability of the composition and abundance of MSFFs as well as the effect of seasonal food availability on their dynamics.Using generalized linear models (GLMs), our results show that the contrasting seasonality in food availability of the study area (using chlorophyll-a concentration as a proxy) had no significant influence on MSFF attributes, sparsely explaining their variations (P>0.05).This would allow them to reduce resource unpredictability, which in turn has a major impact on structuring seabird's MSFF dynamics.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Ecología y Biodiversidad, Facultad de Ecología y Recursos Naturales, Universidad Andrés Bello, Santiago, Chile.

ABSTRACT
The formation of multi-species feeding flocks (MSFFs) through visual recruitment is considered an important strategy for obtaining food in seabirds and its functionality has been ascribed to enhanced foraging efficiency. Its use has been demonstrated in much of the world's oceans and includes numerous species. However, there is scant information on the temporal stability of the composition and abundance of MSFFs as well as the effect of seasonal food availability on their dynamics. Between July 2006 and September 2014, we conducted monthly at-sea seabird counts at Valparaiso Bay (32°56' to 33°01'S, 71°36' to 71°46'W) within the area of influence of the Humboldt Current in central Chile. This area is characterized by a marked seasonality in primary and secondary production associated with upwelling, mainly during austral spring-summer. Based on studies that provide evidence that flocking is most frequent when food is both scarce and patchy, we hypothesized that seabird MSFF attributes (i.e. frequency of occurrence, abundance and composition) will be modified according to the seasonal availability of food. Using generalized linear models (GLMs), our results show that the contrasting seasonality in food availability of the study area (using chlorophyll-a concentration as a proxy) had no significant influence on MSFF attributes, sparsely explaining their variations (P>0.05). Rather than seasonal food availability, the observed pattern for MSFF attributes at Valparaiso Bay suggests a substantial influence of reproductive and migratory (boreal and austral migrants) habits of birds that modulates MSFF dynamics consistently throughout the whole year in this highly variable and patchy environment. We highlight the importance of visual recruitment as a mechanism by which migratory and resident birds interact. This would allow them to reduce resource unpredictability, which in turn has a major impact on structuring seabird's MSFF dynamics.

No MeSH data available.