INVESTIGADORES
MERMOZ Myriam Emilia
artículos
Título:
Effects of nest-ste characteristics and parental activity on cowbird parasitism and nest predation in Brown-and-yellow Marshbirds
Autor/es:
SVAGELJ, W. S.; FERNÁNDEZ, G. J..; MERMOZ, M. E.
Revista:
JOURNAL OF FIELD ORNITHOLOGY
Editorial:
Association of Field Ornithology
Referencias:
Año: 2009 vol. 80 p. 13 - 22
ISSN:
0273-8570
Resumen:
ABSTRACT. Nest-site selection and nest defense are strategies for reducing the costs of brood parasitism
and nest predation, two selective forces that can influence avian nesting success and fitness. During 20012002,
we analyzed the effect of nest-site characteristics, nesting pattern, and parental activity on nest predation and
brood parasitism by cowbirds (Molothrus spp.) in a population of Brown-and-yellow Marshbirds (Pseudoleistes
virescens) in the Buenos Aires province, Argentina. We examined the possible effects of nest detectability, nest
accessibility, and nest defense on rates of parasitism and nest predation. We also compared rates of parasitism
and nest predation and nest survival time of marshbird nests during the egg stage (active nests) with those of
the same nests artificially baited with passerine eggs after young fledged or nests failed (experimental nests). Most
nests (45 of 48, or 94%) found during the building or laying stages were parasitized, and 79% suffered at least
one egg-predation event. Cowbirds were responsible for most egg predation, with 82 of 107 (77%) egg-predation
events corresponding to eggs punctured by cowbirds. Nests built in thistles had higher rates of parasitism and egg
predation than nests in other plant, probably because cowbirds were most active in the area where thistles were
almost the only available nesting substrate. Parasitism rates also tended to increase as the distance to conspecific
nests increased, possibly due to cooperative mobbing and parental defense by marshbirds. The proportion of
nests discovered by cowbirds was higher for active (95%) than for experimental (29%) nests, suggesting that
cowbirds used host parental activity to locate nests. Despite active nest defense, parental activity did not affect
either predation rates or nest-survival time. Thus, although nest defense by Brown-and-yellow Marshbirds appears
to be based on cooperative group defense, such behavior did not reduce the impact of brood parasites and
predators.Molothrus spp.) in a population of Brown-and-yellow Marshbirds (Pseudoleistes
virescens) in the Buenos Aires province, Argentina. We examined the possible effects of nest detectability, nest
accessibility, and nest defense on rates of parasitism and nest predation. We also compared rates of parasitism
and nest predation and nest survival time of marshbird nests during the egg stage (active nests) with those of
the same nests artificially baited with passerine eggs after young fledged or nests failed (experimental nests). Most
nests (45 of 48, or 94%) found during the building or laying stages were parasitized, and 79% suffered at least
one egg-predation event. Cowbirds were responsible for most egg predation, with 82 of 107 (77%) egg-predation
events corresponding to eggs punctured by cowbirds. Nests built in thistles had higher rates of parasitism and egg
predation than nests in other plant, probably because cowbirds were most active in the area where thistles were
almost the only available nesting substrate. Parasitism rates also tended to increase as the distance to conspecific
nests increased, possibly due to cooperative mobbing and parental defense by marshbirds. The proportion of
nests discovered by cowbirds was higher for active (95%) than for experimental (29%) nests, suggesting that
cowbirds used host parental activity to locate nests. Despite active nest defense, parental activity did not affect
either predation rates or nest-survival time. Thus, although nest defense by Brown-and-yellow Marshbirds appears
to be based on cooperative group defense, such behavior did not reduce the impact of brood parasites and
predators.) in the Buenos Aires province, Argentina. We examined the possible effects of nest detectability, nest
accessibility, and nest defense on rates of parasitism and nest predation. We also compared rates of parasitism
and nest predation and nest survival time of marshbird nests during the egg stage (active nests) with those of
the same nests artificially baited with passerine eggs after young fledged or nests failed (experimental nests). Most
nests (45 of 48, or 94%) found during the building or laying stages were parasitized, and 79% suffered at least
one egg-predation event. Cowbirds were responsible for most egg predation, with 82 of 107 (77%) egg-predation
events corresponding to eggs punctured by cowbirds. Nests built in thistles had higher rates of parasitism and egg
predation than nests in other plant, probably because cowbirds were most active in the area where thistles were
almost the only available nesting substrate. Parasitism rates also tended to increase as the distance to conspecific
nests increased, possibly due to cooperative mobbing and parental defense by marshbirds. The proportion of
nests discovered by cowbirds was higher for active (95%) than for experimental (29%) nests, suggesting that
cowbirds used host parental activity to locate nests. Despite active nest defense, parental activity did not affect
either predation rates or nest-survival time. Thus, although nest defense by Brown-and-yellow Marshbirds appears
to be based on cooperative group defense, such behavior did not reduce the impact of brood parasites and
predators.