Short Communication |
Corresponding author: Piotr Tryjanowski ( piotr.tryjanowski@gmail.com ) Academic editor: George Sangster
© 2018 Piotr Tryjanowski, Federico Morelli.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Tryjanowski P, Morelli F (2018) Effects of habitat and time of day on flock size of Turkey Vultures in Cuba (Cathartes aura). ZooKeys 726: 79-86. https://doi.org/10.3897/zookeys.726.14581
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In agricultural landscapes, the Turkey Vulture Cathartes aura feeds mainly on carcases of domestic animals. In spring 2017, data on 214 flocks of Turkey vultures were collected in a road survey in Cuba (in total 2384 km). Turkey Vultures were found to be common accross Cuba, but flock size varied between habitats, reaching a maximum of 43 in valleys and 31 in agricultural landscapes with domestic animal farms. Vultures were active throughout the day, but the time of day did not significantly affect flock size. This study corroborates previous studies which suggested that carrion resources located in agricultural habitats and river valleys is crucial for the continued survival of this still abundant species. Changes in Cuba’s socio-political system in the near future will likely impact agricultural practices, and this in turn will likely affect Turkey Vultures. Our study may serve as a baseline against which future population changes and flocking behaviour of Turkey Vultures can be compared.
Cuba, large-scale survey, roadside, scavenger, vulture
Vultures are globally endangered birds (
The aims of this study were to (1) assess the influence of habitat variation on flock size, (2) describe perches preferred by Turkey Vultures, and (3) assess how the time of the day affects flocking behaviour of the vultures. Results are discussed in the light of the changes expected to occur in the agricultural systems of Cuba due to recent socio-political changes, and which may affect bird populations in a way similar to what occurred in post-communist Europe (
Surveys were conducted from March to April 2017 along roads throughout Cuba (in total 2384 km; Figure
Search effort was determined by habitat availability from the roads. Habitats were classified according to
The associations among flock size, habitat type and time of day were assessed by means of a linear model procedure. Flock size was entered as response variable while time and type of habitat were used as predictors. The model was fitted assuming a log-normal distribution of response variables after having explored the distribution of these variable as suggested by
In total, 1231 individuals in 214 flocks were observed during the study period. Habitat influenced average flock size, with the largest flocks recorded in valleys (43 individuals) and in the vicinity of domestic animal farms (31 individuals) in an agricultural landscape (Figures
Relationship between flock size of Turkey Vultures to habitat type and time of day (N = 214). Abbreviations: 2.5%, lower level of confidence interval; 97.5%, upper level of confidence interval; SE, standard error. The R2 for the model multiple was 0.419.
Variable | Estimate | 2.5% | 97.5% | SE | t | p |
---|---|---|---|---|---|---|
(Intercept) | 2.304 | 1.780 | 2.828 | 0.266 | 8.669 | < 0.05 |
Habitat (open field) | -0.900 | -1.250 | -0.549 | 0.177 | -5.064 | < 0.05 |
Habitat (urban) | -1.002 | -1.354 | -0.649 | 0.178 | -5.609 | < 0.05 |
Habitat (valley) | 0.774 | 0.284 | 1.263 | 0.248 | 3.116 | < 0.05 |
Habitat (village) | -1.457 | -1.779 | -1.136 | 0.163 | -8.924 | < 0.05 |
Habitat (water) | -0.582 | -1.091 | -0.074 | 0.258 | -2.260 | < 0.05 |
Time | -0.014 | -0.049 | 0.017 | 0.016 | -0.886 | n.s. |
A total of 57 perched birds was observed: 32 (56.1%) on trees, eleven (19.3%) sitting on the ground, eight (14.0%) on electric pylons, and six (10.5%) on fences (Figure
Flock size of Turkey Vultures in relation to habitat type. The y-axis represents the estimated variable. The boxplots show the median (bar in middle of rectangles), mean (black rhombus), upper and lower quartiles, and extreme values. The horizontal dashed line is the average values of flock sizes considering all cases.
Turkey vultures feed heavily on carrion of domestic animals in landscapes dominated by agriculture (
In our study, we found the largest flocks near domestic animal farms and in river valleys, where probably carrion of large animals, both wild and domestic, is frequently available. In agreement with previous studies, relatively small numbers of vultures were observed in non-agricultural landscapes. This pattern of flock size related to habitat suggests that the availability carrion of domestic animals is crucial for the vultures’ presence and abundance (
Flying vultures are often noted throughout the day (
During this study, we confirmed previous findings that the Turkey Vulture is still very common in Cuba (
We thank A. Łuczak, P. Kunysz, and J. Tryjanowska for logistical support, and comments by three referees improved the manuscript