排序方式: 共有25条查询结果,搜索用时 0 毫秒
1.
2.
Intraflock variation in the speed of escape-flight response on attack by an avian predator 总被引:7,自引:2,他引:5
The benefits of flocking to prey species, whether through collective
vigilance,dilution of risk, or predator confusion, depend on flock members
respondingin a coordinated way to attack. We videotaped sparrowhawks
attackingredshank flocks to determine if there were differences in thetiming
of escape flights between flock members and the factorsthat might affect any
differences. Sparrowhawks are surpriseshort-chase predators, so variation in
the time taken to takeflight on attack is likely to be a good index of
predation risk.Most birds in a flock flew within 0.25 s of the first bird
flying,and all birds were flying within 0.7 s. Redshanks that werevigilant,
that were closest to the approaching raptor, and thatwere close to their
neighbors took flight earliest within aflock. Birds in larger flocks took
longer, on average, to takeflight, measured from the time that the first bird
in the flockflew. Most birds took flight immediately after near neighbors
tookoff, but later flying birds were more likely to fly immediatelyafter
more distant neighbors took flight. This result, alongwith the result that
increased nearest neighbor distance increasedflight delay, suggests that most
redshanks flew in responseto conspecifics flying. The results strongly
suggest that thereis significant individual variation in predation risk
withinflocks so that individuals within a flock will vary in benefitsthat
they gain from flocking. 相似文献
3.
Indrikis Krams Dina Cirule Valerija Suraka Tatjana Krama Markus J. Rantala Gary Ramey 《Functional ecology》2010,24(1):172-177
1. In a seasonal environment, subcutaneous energy reserves of resident animals often increase in winter and decline again in summer reflecting gradual seasonal changes in their fattening strategies. We studied changes in body reserves of wintering great tits in relation to their dominance status under two contrasting temperature regimes to see whether individuals are capable of optimizing their body mass even under extreme environmental conditions.
2. We predicted that dominant individuals will carry a lesser amount of body reserves than subordinate great tits under mild conditions and that the body reserves of the same dominant individuals will increase and exceed the amount of reserves of subordinates under conditions of extremely low ambient temperatures, when ambient temperature dropped down to −37 °C.
3. The results confirmed the predictions showing that dominant great tits responded to the rising risk of starvation under low temperatures by increasing their body reserves and this was done at the expense of their safety.
4. Removal experiments revealed that lower body reserves of subordinate flock members are due to the increased intraspecific competition for food under low ambient temperatures.
5. Our results also showed that fattening strategies of great tits may change much quicker than previously considered, reflecting an adaptive role of winter fattening which is sensitive to changes in ambient temperatures. 相似文献
2. We predicted that dominant individuals will carry a lesser amount of body reserves than subordinate great tits under mild conditions and that the body reserves of the same dominant individuals will increase and exceed the amount of reserves of subordinates under conditions of extremely low ambient temperatures, when ambient temperature dropped down to −37 °C.
3. The results confirmed the predictions showing that dominant great tits responded to the rising risk of starvation under low temperatures by increasing their body reserves and this was done at the expense of their safety.
4. Removal experiments revealed that lower body reserves of subordinate flock members are due to the increased intraspecific competition for food under low ambient temperatures.
5. Our results also showed that fattening strategies of great tits may change much quicker than previously considered, reflecting an adaptive role of winter fattening which is sensitive to changes in ambient temperatures. 相似文献
4.
5.
6.
Group foragers may assess patch quality more efficiently bypaying
attention to the sampling behavior of group members foragingin the same patch
(i.e., using "public information"). To determinewhether red
crossbills (Loxia curvirostra) use public informationto aid their
patch departure decisions, we conducted experimentsthat compared the sampling
behavior of crossbills foraging ona two-patch system (one patch was always
empty, one patch containingseeds) when alone, in pairs, and in flocks of
three. When foragingalone, crossbills departed from empty patches in a way
thatwas qualitatively consistent with energy maximization. We foundevidence
for the use of public information when crossbills werepaired with two flock
mates, but not when paired with one flockmate. When foraging with two flock
mates, crossbills sampledapproximately half the number of cones on the empty
patch beforedeparting as compared to when solitary. Furthermore, as expected
ifpublic information is used, the variance in both the numberof cones and
time spent on the empty patch decreased when crossbillsforaged with two flock
mates as compared to when alone. Althoughhigh frequencies of scrounging
reduce the availability of publicinformation, scrounging is usually uncommon
in crossbills, apparentlybecause they exploit divisible patches.
Consequently, publicinformation is likely to be important to crossbills in
the wild.We also show that feeding performance is greatly diminishedwhen the
feeding performances of flock mates differ. This providesa mechanism that
will favor assortative grouping by phenotypewhen phenotypes affect feeding
performance, which may in turnpromote speciation in some groups of
animals. 相似文献
7.
Summary We tested two general models of flocking behaviour, namely the antipredation model and foraging efficiency model on mixed-species tit flocks (Parus spp.). After food addition the size of mixed-species flocks was significantly less than in the control samples. In the presence of extra food significantly more birds were observed either in monospecific flocks or solitary, than during the control observations. In the presence of a living predator the birds foraged in larger mixed-specifies flocks than during the control observations. In addition, the social behaviour of Great Spotted Woodpecker, Middle Spotted Woodpecker and Nuthatch shifted to mixed-specific flocking. The size of monospecific flocks was independent of both treatments. The density of birds increased significantly after food addition, while in the predator presence the birds tended to leave the forest. These results support the view that both the antipredation model and foraging efficiency model seem to be valid for mixed-species flocking. However, in the case of monospecific flocks, the territory maintenance could be the most important factor. 相似文献
8.
9.
10.