Seasonal change in tropical habitat quality and body condition for a declining migratory songbird

McKinnon, Emily A.; Rotenberg, James A.; Stutchbury, Bridget J. M.

doi:10.1007/s00442-015-3343-1

Cited by 38 publications

(51 citation statements)

References 55 publications

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“…These results contradict the findings of Holmes et al (1996) and Johnson et al (2006). The less-than-expected variation in fat storage among the three habitats in our study, other than the harshest (scrub), parallels the results of a recent study of Wood Thrushes (Hylocichla mustelina) overwintering in Belize (McKinnon et al 2015) where birds were found to be in equally poor body condition in each of three habitats due to late-winter drying and reduced abundance of arthropods and fruits. Another possible source of variation in SFD that may have obscured patterns, and which our study was not designed to detect, is subtle within-habitat variation in wintering strategy, particularly by species of wintering migrants, especially transient versus territorial behavior.…”

Section: Discussionsupporting

confidence: 89%

“…Holmes et al (1996) reported that more experienced and socially dominant older birds generally preempted first-winter birds from high-quality habitats. Birds in lower-quality habitats with unpredictable food availability may store more fat as a hedge against fasting (Lima 1986), although late-winter (dry season) food reduction has been shown to reduce SFD in migrants wintering in Jamaican mangrove habitat (Brown and Sherry 2006) and other Caribbean forests (McKinnon et al 2015). Assessing these SFD predictions for environmental and demographic variables requires precise estimates of actual body fat content in wintering birds.…”

Section: Introductionmentioning

confidence: 99%

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Effects of habitat, season, and age on winter fat storage by migrant and resident birds in Jamaica

2019

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Most small birds wintering in the tropics should show little subcutaneous fat deposition (SFD), except in habitats where food availability may decline in late winter or, for some resident species, to prepare for incubation or brooding fasts. However, these predictions need re‐examination in light of a new, precise, cross‐validated method to compare SFD among habitats and species. We sampled 170 Nearctic‐Neotropical migrant and 279 resident birds during early and late winter in 1993 and 1994 in Jamaica, West Indies. Habitats, from greatest to least expected availability of insect prey, were (1) mangrove forest, (2) montane/foothills forest and cultivation, (3) dry limestone forest, and (4) acacia scrub. Percent lipid, estimated from multiple‐regression models using visual fat scoring (0–8 scale), total‐body electrical conductivity, and a variety of morphometrics, was categorized by percentile ranks to determine if SFD varied by habitat, season, or age for all species, resident species, migrant species, and several individual species. SFD averaged ~ 13% total mass for all birds, ranging from 8–24% for well‐sampled species. The few bird species in acacia scrub, primarily two facultative long‐distance migrants, averaged ~ 26% lipid content, significantly more than birds in other habitats. Most birds did not vary in SFD in the other three habitats, although Common Yellowthroats (Geothlypis trichas) had greater SFD in dry limestone habitat than in montane habitat. Bananaquits (Coereba flaveola) and Jamaican Euphonias (Euphonia jamaica) in montane habitat, especially in early winter, had higher SFD than other resident species. Contrary to our prediction, adults and juveniles had similar SFD, with the exception of juveniles having more SFD than adults in acacia scrub habitat. Winter fat deposition (or, in some cases, muscle‐protein catabolism) in the tropics may be an overlooked strategy, potentially important as a hedge against fasting for floaters, facultative migrants, some territorial migrants in habitats with seasonal declines in food resources, and some resident species prior to breeding.

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Section: Discussionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Effects of habitat, season, and age on winter fat storage by migrant and resident birds in Jamaica

2019

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“…However, it remains unclear how interactions between habitat quality on winter grounds and associated carryover effects (McKinnon et al. ) coupled with limiting factors on the breeding grounds, including negative effects of cowbird parasitism we have demonstrated, may ultimately limit populations. In addition to improved knowledge on migratory connectivity, full‐annual‐cycle population models require accurate demographic data, which are largely absent for many species, and have proven challenging to collect over long time periods and across large spatial scales.…”

Section: Discussionmentioning

confidence: 93%

Long‐term dynamics in local host–parasite interactions linked to regional population trends

et al. 2016

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Abstract. Temporal changes in the relative abundances of host-parasite populations can influence the magnitude of the effects of corresponding interspecific interactions. When parasite populations are at relatively low abundance, the negative effects on host populations may be insignificant, but when parasite abundance increases beyond critical thresholds, they can have population limiting effects on the host. Here, we used data from a 40-yr demographic study on breeding Wood Thrushes (Hylocichla mustelina) and avian brood parasitic Brown-headed Cowbirds (Molothrus ater) in the mid-Atlantic United States to disentangle host-parasite interactions. The relative abundance for these two species has changed both locally and regionally over this time period with a reduction in host abundance coincident with an increase in the parasite population. We detected a fivefold increase in Brown-headed Cowbird parasitism rates of Wood Thrushes over the 40-yr time period leading to a reduction in Wood Thrush fitness (i.e., adult survival, fecundity, and recruitment). After accounting for the effects of Wood Thrush age, individual, and annual and within-season variation in reproduction, we found that Wood Thrushes exhibited increased reproductive effort (produced more nests per year) as nest parasitism rates increased. Additionally, we found that as parasitism rates increased, both Wood Thrush clutch size and fecundity declined. In conjunction with widespread habitat loss and land use change on both wintering and breeding ranges, increasing rates of Brown-headed Cowbird parasitism are reducing Wood Thrush fitness, and are likely contributing to observed regional Wood Thrush population declines. Coordinated local and regional efforts to reduce Brown-headed Cowbird populations, particularly in fragmented landscapes, may help reduce the decline for Wood Thrushes, and likely other parasitized Neotropical migratory species.

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“…, McKinnon et al. ). Because arthropod abundance is correlated with habitat moisture, availability of arthropods may decline during the overwintering period of migratory birds (Strong and Sherry , Smith et al.…”

mentioning

confidence: 99%

Does the proportion of arthropods versus fruit in the diet influence overwintering condition of an omnivorous songbird?

2017

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ABSTRACT. Many migratory songbirds switch from a primarily insectivorous diet during the breeding season to either a mixed diet or fruit diet during the non-breeding season. However, for species with mixed diets, arthropods may be superior food items because of their higher protein content and easier digestibility. We tested this hypothesis by analyzing the diet and body condition of omnivorous Wood Thrushes (Hylocichla mustelina) at a non-breeding site in tropical forest in Belize, Central America. We used analysis of stable isotopes d 15 N and d 13 C in the blood to measure diet. Our objective was to determine if a higher dietary proportion of arthropods relative to fruit (i.e., higher d 15 N and d 13 C) was associated with better body condition. We also examined the possible effect of age, sex, and habitat type on Wood Thrush diets, as well as any changes in diet through the overwintering period. We used a hierarchical Bayesian mixing model (MixSIAR) to estimate the proportion of different prey items in the diet of overwintering Wood Thrushes overall, in each habitat type, and over time during the non-breeding period. From January to April, we found a significant decline in d 15 N in forest habitats, whereas d 15 N increased in scrub habitat. There was no significant seasonal change in d 13 C. Birds with higher d 15 N or d 13 C values were not in better body condition. Females in dry-scrub habitat consumed more fruit than males, but this did not affect body condition. Mixing model results indicated that most Wood Thrushes at our study sites consumed primarily arthropods, even during the driest times of the non-breeding season and in the driest habitat. Overall, our results suggest that the diet of Wood Thrushes varies with habitat and during the overwintering period, but diet alone was not a predictor of body condition. Wood Thrushes, and possibly other omnivorous migratory songbirds, are apparently flexibly able to meet their wintering and pre-migration nutritional demands with a variety of diets.RESUMEN. La proporci on de artr opodos versus frutas en la dieta influencia la condici on f ısica durante el invierno en un ave canora omn ıvora? Muchas aves canoras migratorias cambian de una dieta principalmente insect ıvora durante la temporada reproductiva a una dieta o bien mixta o bien frug ıvora durante la temporada no reproductiva. A un as ı, para especies con dietas mixtas, los artr opodos pueden ser items alimentarios superiores debidos a su mayor contenido prot eico y f acil digesti on. Pusimos a prueba esta hip otesis analizando la dieta y la condici on f ısica del omn ıvoro Zorzal del Bosque (Hylocichla mustelina) en un sitio no reproductivo en el bosque tropical de Belize, Am erica Central. Utilizamos an alisis de is otopos estables d 15 N y d 13 C en la sangre a fin de medir dieta. Nuestro objetivo fue determinar si una proporci on m as alta de artropodos en relaci on a fruta en la dieta (i.e., d15 N y d 13 C m as alto) est a asociada con una mejor condici on f ısica. Examinamos tambi en el posible ef...

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Seasonal change in tropical habitat quality and body condition for a declining migratory songbird

Cited by 38 publications

References 55 publications

Effects of habitat, season, and age on winter fat storage by migrant and resident birds in Jamaica

Effects of habitat, season, and age on winter fat storage by migrant and resident birds in Jamaica

Long‐term dynamics in local host–parasite interactions linked to regional population trends

Does the proportion of arthropods versus fruit in the diet influence overwintering condition of an omnivorous songbird?

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