Interference asymmetries among age-sex classes of rufous hummingbirds during migratory stopovers

Carpenter, F. Lynn; Hixon, Mark A.; Russell, Robert W.; Paton, David C.; Temeles, Ethan J.

doi:10.1007/bf00172927

Cited by 57 publications

(57 citation statements)

References 41 publications

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“…When intruders enter territories, they take food but do not challenge residents for ownership, and residents do not lose ownership to intruders (cf. Davies & Houston 1981;Tricas 1989;Carpenter et al 1993b;Temeles 1994). Residents inhabit their territories for a finite period of time, and they can accurately predict the duration of residency and the time when they will abandon their territories.…”

Section: Model Formulation and Methodsmentioning

confidence: 99%

“…For example, rufous hummingbirds, Selasphorus rufus, establish feeding territories at stopovers during migration, and then voluntarily abandon these territories when they reach a condition that allows them to resume migration (Carpenter et al 1983(Carpenter et al , 1993b. Carpenter et al (1993a) were able to predict when individual hummingbirds would abandon their territories, based on relaxation of territorial defence by residents the day before they resumed migration.…”

Section: Dynamic Versus Static Models Of Territory Defencementioning

confidence: 99%

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When should a territory resident attack?

2001

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Models of territorial defence tend to omit two characteristics of many territorial systems: repeated intrusions by the same individual and the learning processes of residents and intruders. Here we present state-dependent, dynamic models of feeding territories, designed to investigate temporal patterns of resident aggression towards intruders that are capable of spatial learning. We compare two types of models: (1) a nomadic intruder model, in which intruders never visit the same territory twice, and (2) a single, repeat intruder model, in which an intruder may repeatedly intrude into a given territory but is less likely to do so after being attacked. These two models produce qualitatively and quantitatively different patterns of aggression by residents. For instance, residents with intruders that may repeatedly intrude have high initial attack rates, regardless of initial probability of intrusion, but their attack rates decline over time. In contrast, residents in the nomadic intruder model do not attack intruders if intrusion rates are moderately high, and their attack rates are constant and high for most of the period of territory tenure. In addition, residents of both nomadic and repeat intruder scenarios stopped attacking intruders for a short period before voluntarily abandoning their feeding territories. The results of our models suggest that repeated intrusions and learning processes have a dramatic effect on territorial defence.  2001 The Association for the Study of Animal BehaviourFor many years, models have played an important role in advancing our understanding of the role of aggression in territorial species. However, a dichotomy has arisen between models investigating territories and models investigating aggressive behaviour. Most territory models focus on an individual versus the rest of the population, and consider such questions as when space should be defended, how much space should be defended, or what shape a territory should be (e.g.

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Section: Model Formulation and Methodsmentioning

confidence: 99%

Section: Dynamic Versus Static Models Of Territory Defencementioning

confidence: 99%

When should a territory resident attack?

2001

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“…The high metabolic rate of hummingbirds (Berger, 1985) and their competitive aggression when food resources are potentially limited (Carpenter et al, 1993) allowed us to vary hummingbird motivation for initiating flight. We report on leg forces and kinematics measured during take-off in rufous hummingbirds (Selasphorus rufus Gmelin) as the birds initiated flight in three motivational states: autonomously to feed, startled to escape a hand movement, and aggressively to chase a conspecific from a feeder.…”

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Take-off mechanics in hummingbirds (Trochilidae)

Tobalske

Altshuler

Powers

2004

Journal of Experimental Biology

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Initiating flight is challenging, and considerable effort has focused on understanding the energetics and aerodynamics of take-off for both machines and animals. For animal flight, the available evidence suggests that birds maximize their initial flight velocity using leg thrust rather than wing flapping. The smallest birds, hummingbirds (Order Apodiformes), are unique in their ability to perform sustained hovering but have proportionally small hindlimbs that could hinder generation of high leg thrust. Understanding the take-off flight of hummingbirds can provide novel insight into the take-off mechanics that will be required for micro-air vehicles. During take-off by hummingbirds, we measured hindlimb forces on a perch mounted with strain gauges and filmed wingbeat kinematics with high-speed video. Whereas other birds obtain 80-90% of their initial flight velocity using leg thrust, the leg contribution in hummingbirds was 59% during autonomous take-off. Unlike other species, hummingbirds beat their wings several times as they thrust using their hindlimbs. In a phylogenetic context, our results show that reduced body and hindlimb size in hummingbirds limits their peak acceleration during leg thrust and, ultimately, their takeoff velocity. Previously, the influence of motivational state on take-off flight performance has not been investigated for any one organism. We studied the full range of motivational states by testing performance as the birds took off: (1) to initiate flight autonomously, (2) to escape a startling stimulus or (3) to aggressively chase a conspecific away from a feeder. Motivation affected performance. Escape and aggressive take-off featured decreased hindlimb contribution (46% and 47%, respectively) and increased flight velocity. When escaping, hummingbirds foreshortened their body movement prior to onset of leg thrust and began beating their wings earlier and at higher frequency. Thus, hummingbirds are capable of modulating their leg and wingbeat kinetics to increase take-off velocity.

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“…This 2 p(b/2) definition explicitly assumes that the wings rotate about a point in the center of the body and that each wing flaps through a stroke amplitude of 180Њ. A definition of WDL conforming to the above criteria has been repeatedly used as a surrogate measure for induced power requirements in hovering (Epting and Casey 1973;Feinsinger and Chaplin 1975;Feinsinger and Colwell 1978;Feinsinger et al 1979;Epting 1980;Carpenter et al 1993b). However, this model contains several uncorroborated assumptions.…”

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confidence: 99%

Of Hummingbirds and Helicopters: Hovering Costs, Competitive Ability, and Foraging Strategies

Altshuler¹,

Stiles²,

Dudley³

2004

The American Naturalist

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Wing morphology and flight kinematics profoundly influence foraging costs and the overall behavioral ecology of hummingbirds. By analogy with helicopters, previous energetic studies have applied the momentum theory of aircraft propellers to estimate hovering costs from wing disc loading (WDL), a parameter incorporating wingspan (or length) and body mass. Variation in WDL has been used to elucidate differences either among hummingbird species in nectar-foraging strategies (e.g., territoriality, traplining) and dominance relations or among gender-age categories within species. We first demonstrate that WDL, as typically calculated, is an unreliable predictor of hovering (induced power) costs; predictive power is increased when calculations use wing length instead of wingspan and when actual wing stroke amplitudes are incorporated. We next evaluate the hypotheses that foraging strategy and competitive ability are functions of WDL, using our data in combination with those of published sources. Variation in hummingbird behavior cannot be easily classified using WDL and instead is correlated with a diversity of morphological and physiological traits. Evaluating selection pressures on hummingbird wings will require moving beyond wing and body mass measurements to include the assessment of the aerodynamic forces, power requirements, and power reserves of hovering, forward flight, and maneuvering. However, the WDL- helicopter dynamics model has been instrumental in calling attention to the importance of comparative wing morphology and related aerodynamics for understanding the behavioral ecology of hummingbirds.

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Interference asymmetries among age-sex classes of rufous hummingbirds during migratory stopovers

Cited by 57 publications

References 41 publications

When should a territory resident attack?

When should a territory resident attack?

Take-off mechanics in hummingbirds (Trochilidae)

Of Hummingbirds and Helicopters: Hovering Costs, Competitive Ability, and Foraging Strategies

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