Variation in Aggression of Black-throated Blue Warblers Wintering in Jamaica

Abstract

Variation in aggression among birds on different territories has been hypothesized to be influenced by intrinsic factors such as a bird's age, sex, or size and extrinsic factors such as density of neighbors, abundance of food, or territory size. However, little work has examined how and why aggression may vary within a bird's home range. We examined variation in aggressive behaviors of nonbreeding Black-throated Blue Warblers {Setophaga caerulescens) in Jamaican coffee farms by using experimentally simulated intrusions into home ranges. Our multivariate models confirmed that multiple variables associated with aggression included sex, home range size, proximity of intrusion to home range center, and the presence of another aggressive bird in the area. In addition, we found that birds responded more aggressively to intrusions in shade trees, where insects were more abundant, than in the understory of coffee or of small patches of remnant forest. These results suggest the birds responded to variation in habitat and/or food supply within their home ranges and varied aggressive responses accordingly, revealing a finer scale of behavioral resource matching than previously documented for bird territoriality. Variación en la Agresión de Individuos de Setophaga caerulescens que Invernan en JamaicaResumen. Se ha hipotetizado que la variación en la agresión entre las aves en territorios diferentes está influenciada por factores intrínsecos como la edad del ave, el sexo y el tamaño, y por factores extrínsecos como la densidad de vecinos, la abundancia de alimentos o el tamaño del territorio. Sin embargo, poco se ha examinado cómo y por qué la agresión puede variar dentro del área de acción de un ave. Examinamos la variación en los comportamientos de agresión de individuos no reproductivos de Setophaga caerulescens en granjas de café de Jamaica mediante el empleo de simulaciones experimentales de intrusión en las áreas de acción. Nuestros modelos multivariados confirmaron que las variables asociadas con la agresión incluyeron sexo, tamaño del área de acción, proximidad de la intrusión al centro del área de acción y presencia de otra ave agresiva en el área. Adicionalmente, encontramos que las aves respondieron de forma más agresiva a las intrusiones en las plantaciones de café con árboles de sombra, donde los insectos fueron más abundantes, que en las plantaciones sin árboles de sombra o en pequeños parches remanentes de bosque. Estos resultados sugieren que las aves respondieron a variaciones en el habitat o en la provisión de alimentos dentro de sus áreas de acción y que de acuerdo a esto cambiaron sus respuestas agresivas, revelando una escala de más detalle de ajuste del comportamiento a los recursos de lo que se habla documentado previamente para la territorialidad de las aves.

Dietary opportunism, resource partitioning, and consumption of coffee berry borers by five species of migratory wood warblers (Parulidae) wintering in Jamaican shade coffee plantations

“…The difference in diets of male and female Black‐throated Blue Warblers is consistent with use of sex‐specific foraging heights and behaviors in Jamaican coffee farms (i.e., intraspecific niche partitioning, with males disproportionately in the canopy; Smith et al. ), and with stronger aggression to simulated intruders in the food‐rich canopy, particularly by larger males and males in general (Smith et al. ).…”

“…), and with stronger aggression to simulated intruders in the food‐rich canopy, particularly by larger males and males in general (Smith et al. ). Although we detected no difference in their diets, male and female American Redstarts are also ecologically segregated in coffee farms, with females tending to forage more in the coffee shrub layer and males in shaded coffee farms and in the shade trees forming the canopy in these farms (Wunderle and Latta , MD Johnson, pers.…”

Rapid effects of estrogens on behavior: Environmental modulation and molecular mechanisms

“…Nuclear estrogen receptors are assumed to be irrelevant for rapid estrogen action, yet there is strong evidence that estrogens regulate a wide range of social behaviors via nongenomic mechanisms. One such behavior is aggression, which is tightly coupled with reproductive behavior [32-34] and can be critical for maintaining territorial resources necessary for mating opportunities as well guarding potential mates [38, 39]. Estrogens also modulate individual recognition, which can determine whether an individual decides to engage and aggression.…”

Aggressive behavior by Western Bluebirds (Sialia mexicana) varies with anthropogenic disturbance to breeding habitat

“…data). Nor did younger birds respond more aggressively towards the goldfinch than older birds (based on a sample of 21 nests where birds were aged as SY or ASY using molt limits: males: W 5 15.5, P 5 0.24, n 5 17; females: W 5 31.5, P 5 0.23, n 5 15), as might be expected if age or inexperience was a cause of this pattern (Smith et al 2012). In similar experiments conducted by Duckworth (2006b), aggressive response of Western Bluebirds to a non-competitor species (House Finch, Carpodacus mexicanus) was always low.…”