Winter irruption of two Geranoaetus hawks in the Monte Desert of Argentina
Winter irruption refers to an unpredictable increase in the number of individuals usually dominated by one age class, either juvenile or adult, into a given area as a response to fluctuations in the food supply. Irruptions are well documented for avian predators breeding in the Arctic and Subarctic...
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ftconicet:oai:ri.conicet.gov.ar:11336/205265 2023-10-09T21:49:33+02:00 Winter irruption of two Geranoaetus hawks in the Monte Desert of Argentina Juhant, Matias Alejandro Terrien, Jean-François Areta, Juan Ignacio application/pdf http://hdl.handle.net/11336/205265 eng eng Raptor Research Foundation info:eu-repo/semantics/altIdentifier/doi/10.3356/JRR-20-121 http://hdl.handle.net/11336/205265 Juhant, Matias Alejandro; Terrien, Jean-François; Areta, Juan Ignacio; Winter irruption of two Geranoaetus hawks in the Monte Desert of Argentina; Raptor Research Foundation; Journal of Raptor Research; 56; 2; 6-2022; 180-189 0892-1016 CONICET Digital CONICET info:eu-repo/semantics/restrictedAccess https://creativecommons.org/licenses/by-nc-sa/2.5/ar/ AGE CLASSES BLACK-CHESTED BUZZARD-EAGLE GERANOAETUS MELANOLEUCUS GERANOAETUS POLYOSOMA NONBREEDING SEASON SEMIARID GRASSLAND SHRUB STEPPES SOUTH AMERICA VARIABLE HAWK https://purl.org/becyt/ford/1.6 https://purl.org/becyt/ford/1 info:eu-repo/semantics/article info:ar-repo/semantics/artículo info:eu-repo/semantics/publishedVersion ftconicet https://doi.org/10.3356/JRR-20-121 2023-09-24T19:15:45Z Winter irruption refers to an unpredictable increase in the number of individuals usually dominated by one age class, either juvenile or adult, into a given area as a response to fluctuations in the food supply. Irruptions are well documented for avian predators breeding in the Arctic and Subarctic regions whereby individuals irrupt into irregular nonbreeding areas across the Boreal Temperate Region. However, this phenomenon is largely unknown across the Austral Temperate Region. We studied the age class composition of Variable Hawks (Geranoaetus polyosoma) and Black-chested Buzzard-Eagles (G. melanoleucus) during six austral winters (nonbreeding season) at an overlapping breeding and overwintering area in the Monte Desert (semiarid grassland and shrub steppes) of the Andean foothills at Mendoza province in central Argentina (33°S). We measured the overall abundance per winter (combining the five age classes) and calculated the relative abundance per age class for each winter of both species. We used the ratio of total number of individuals observed in a single winter/the total hours of observation per winter as an index of abundance, because sampling effort was not equal across winters. We found that (1) both species exhibited winter irruptions, (2) the irruptions were largely driven by a marked increase of Basic I individuals (the youngest age class); at the same time, Basic V individuals (the oldest age class) exhibited their (modestly) lowest abundance, and (3) winter irruptions might be species-specific, as the responses differed between the two species, with a joint irruption event in the austral winter 2016 and a second irruptive event only recorded for Black-chested Buzzard-Eagles in the austral winter of 2018. We posit that the marked increase of Basic I individuals during the irruptive winters cannot be fully explained by successful breeding of the local population, and is likely largely a result of individuals born elsewhere, presumably at southern latitudes, and overwintering at our study site in ... Article in Journal/Newspaper Arctic Subarctic CONICET Digital (Consejo Nacional de Investigaciones Científicas y Técnicas) Arctic Austral Argentina Journal of Raptor Research 56 2 |
institution |
Open Polar |
collection |
CONICET Digital (Consejo Nacional de Investigaciones Científicas y Técnicas) |
op_collection_id |
ftconicet |
language |
English |
topic |
AGE CLASSES BLACK-CHESTED BUZZARD-EAGLE GERANOAETUS MELANOLEUCUS GERANOAETUS POLYOSOMA NONBREEDING SEASON SEMIARID GRASSLAND SHRUB STEPPES SOUTH AMERICA VARIABLE HAWK https://purl.org/becyt/ford/1.6 https://purl.org/becyt/ford/1 |
spellingShingle |
AGE CLASSES BLACK-CHESTED BUZZARD-EAGLE GERANOAETUS MELANOLEUCUS GERANOAETUS POLYOSOMA NONBREEDING SEASON SEMIARID GRASSLAND SHRUB STEPPES SOUTH AMERICA VARIABLE HAWK https://purl.org/becyt/ford/1.6 https://purl.org/becyt/ford/1 Juhant, Matias Alejandro Terrien, Jean-François Areta, Juan Ignacio Winter irruption of two Geranoaetus hawks in the Monte Desert of Argentina |
topic_facet |
AGE CLASSES BLACK-CHESTED BUZZARD-EAGLE GERANOAETUS MELANOLEUCUS GERANOAETUS POLYOSOMA NONBREEDING SEASON SEMIARID GRASSLAND SHRUB STEPPES SOUTH AMERICA VARIABLE HAWK https://purl.org/becyt/ford/1.6 https://purl.org/becyt/ford/1 |
description |
Winter irruption refers to an unpredictable increase in the number of individuals usually dominated by one age class, either juvenile or adult, into a given area as a response to fluctuations in the food supply. Irruptions are well documented for avian predators breeding in the Arctic and Subarctic regions whereby individuals irrupt into irregular nonbreeding areas across the Boreal Temperate Region. However, this phenomenon is largely unknown across the Austral Temperate Region. We studied the age class composition of Variable Hawks (Geranoaetus polyosoma) and Black-chested Buzzard-Eagles (G. melanoleucus) during six austral winters (nonbreeding season) at an overlapping breeding and overwintering area in the Monte Desert (semiarid grassland and shrub steppes) of the Andean foothills at Mendoza province in central Argentina (33°S). We measured the overall abundance per winter (combining the five age classes) and calculated the relative abundance per age class for each winter of both species. We used the ratio of total number of individuals observed in a single winter/the total hours of observation per winter as an index of abundance, because sampling effort was not equal across winters. We found that (1) both species exhibited winter irruptions, (2) the irruptions were largely driven by a marked increase of Basic I individuals (the youngest age class); at the same time, Basic V individuals (the oldest age class) exhibited their (modestly) lowest abundance, and (3) winter irruptions might be species-specific, as the responses differed between the two species, with a joint irruption event in the austral winter 2016 and a second irruptive event only recorded for Black-chested Buzzard-Eagles in the austral winter of 2018. We posit that the marked increase of Basic I individuals during the irruptive winters cannot be fully explained by successful breeding of the local population, and is likely largely a result of individuals born elsewhere, presumably at southern latitudes, and overwintering at our study site in ... |
format |
Article in Journal/Newspaper |
author |
Juhant, Matias Alejandro Terrien, Jean-François Areta, Juan Ignacio |
author_facet |
Juhant, Matias Alejandro Terrien, Jean-François Areta, Juan Ignacio |
author_sort |
Juhant, Matias Alejandro |
title |
Winter irruption of two Geranoaetus hawks in the Monte Desert of Argentina |
title_short |
Winter irruption of two Geranoaetus hawks in the Monte Desert of Argentina |
title_full |
Winter irruption of two Geranoaetus hawks in the Monte Desert of Argentina |
title_fullStr |
Winter irruption of two Geranoaetus hawks in the Monte Desert of Argentina |
title_full_unstemmed |
Winter irruption of two Geranoaetus hawks in the Monte Desert of Argentina |
title_sort |
winter irruption of two geranoaetus hawks in the monte desert of argentina |
publisher |
Raptor Research Foundation |
url |
http://hdl.handle.net/11336/205265 |
geographic |
Arctic Austral Argentina |
geographic_facet |
Arctic Austral Argentina |
genre |
Arctic Subarctic |
genre_facet |
Arctic Subarctic |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.3356/JRR-20-121 http://hdl.handle.net/11336/205265 Juhant, Matias Alejandro; Terrien, Jean-François; Areta, Juan Ignacio; Winter irruption of two Geranoaetus hawks in the Monte Desert of Argentina; Raptor Research Foundation; Journal of Raptor Research; 56; 2; 6-2022; 180-189 0892-1016 CONICET Digital CONICET |
op_rights |
info:eu-repo/semantics/restrictedAccess https://creativecommons.org/licenses/by-nc-sa/2.5/ar/ |
op_doi |
https://doi.org/10.3356/JRR-20-121 |
container_title |
Journal of Raptor Research |
container_volume |
56 |
container_issue |
2 |
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1779312579260186624 |