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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2010.06.024 Byline: Will Cresswell (a), John L. Quinn (b) Abstract: The selective benefits of living in groups may increase with group size but this will depend on predator species or hunting mode. We tested whether the strength of selection for flock size in redshanks, Tringa totanus, depended on hunting mode used by sparrowhawks, Accipiter nisus, and peregrine falcons, Falco peregrinus. Sparrowhawks prefer to ambush prey from cover, whereas peregrines normally attack from the open and use aerial pursuit. The success rate of surprise attacks should always decline with group size because of vigilance effects, and so should be similar for both predators. The success rate of nonsurprise attacks should decline with group size for peregrines because confusion effects apply, but not necessarily for sparrowhawks which quickly give up their chase. Consequently, peregrines should be more likely to attack smaller flocks than sparrowhawks to minimize confusion. Observations of 895 attacks, including 120 captures, confirmed these predictions. The decline in success rate with group size was the same for both predators for surprise attacks but was seen only for peregrines for nonsurprise attacks. Sparrowhawks attacked larger flocks than peregrines, although both species attacked small flocks with similar frequency. Our results suggest that the selective benefits of group size depend both on predator type and hunting mode, we assume because of variation in the importance of vigilance and confusion, and on relative predator abundance. Changes in prey group size may then change the strength of selection on vigilance and confusion effects by altering the relative attack frequency by different predators. Author Affiliation: (a) School of Biology, University of St Andrews, U.K. (b) Edward Grey Institute, Department of Zoology, University of Oxford, U.K. Article History: Received 29 April 2010; Revised 18 May 2010; Accepted 21 June 2010 Article Note: (miscellaneous) MS. number: 10-00290R

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2007.11.005 Byline: Alex Sansom, Will Cresswell, Jeroen Minderman, Johan Lind Abstract: Animals gain antipredation benefits from being in larger groups through increased probability of predator detection, dilution of individual risk of being attacked and confusion of predators during attack. A further benefit is that individuals in larger groups can decrease the amount of time they spend being vigilant, while maintaining a high probability of predator detection. They may then gain extra time to forage, so increasing overall intake rate. Increasing group size, however, can also increase competition so that intake rates decrease. We investigated whether there was a foraging benefit in redshanks, Tringa totanus, that show the group size decrease in individual vigilance. Intake rates did not change with group size, despite an increase in time spent foraging. Interference competition increased with group size because individuals travelled more to find prey. Redshanks used the extra time available to forage to maintain intake rates under increased competition. Although the group size effect on vigilance did not accrue direct foraging benefits, larger groups formed, conferring other antipredation benefits. Intake rates were maintained because the interference competition was compensated by the benefits of reduced individual vigilance. Author Affiliation: (a) School of Biology, University of St. Andrews, U.K. (a ) School of Biology & Psychology, Newcastle University, U.K. (a ) Department of Zoology, Stockholm University, Sweden Article History: Received 8 June 2007; Revised 6 August 2007; Accepted 13 November 2007 Article Note: (miscellaneous) MS. number: 9411R

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2004.10.007 Byline: John L. Quinn, Will Cresswell Abstract: Variation in escape response delays can be explained by at least two, nonmutually exclusive hypotheses: (1) the perceptual limit hypothesis, where delays result because of physical constraints related to predator detection and alarm signal transmission, and (2) the economic hypothesis, where delays are adaptive because they help to avoid superfluous, or to optimize essential, escape responses. We explored the relative importance of these effects in determining first response delays (the time elapsed between the 'detectors' leaving and the start of the rest of the flock's escape) and main response delays (time taken for all nondetectors to escape) among redshank flocks to three stimuli that posed different levels of risk (an attacking hawk, an approaching harmless species and a stimulus that did not involve any obvious external threat). There was strong support for the economic hypothesis because first response delays increased with flock size during responses to low-risk stimuli, when we assume the cost of not escaping immediately was lower because of increasing benefits from the dilution and confusion effects. There was also strong support for the perceptual limit hypothesis because main response delays were explained entirely by spacing and got quicker as flock size increased. This suggests that, once the rest of the flock started to respond to the detectors, benefits gained through the dilution and confusion effects decreased rapidly, so that immediate escape was the optimal response. Escape response delays can therefore be explained by both hypotheses and we discuss the implications of our results for group-living theory. Author Affiliation: (*) Edward Grey Institute, Department of Zoology, University of OxfordU.K. (a ) School of Biology, University of St AndrewsU.K. Article History: Received 31 May 2004; Revised 3 July 2004; Accepted 7 October 2004 Article Note: (miscellaneous) MS. number: 8147R

Wide ranging birds have a greater mass-dependent risk of predation than more sedentary birds. European blackbirds were examined to determine whether they had a low mass than more sedentary birds. Blackbirds that travelled shorter distances and less often to a feeder had the higher mass midwinter, compared to their spring mass. The link between distance travelled and mass may be independent of food supply.

Nest characteristics, clutch size and parental behavior have differential effects on nest predation rates in blackbirds, Turdus merula. Nest predation rates during the egg stage are the same for natural nests with parents and artificial clutches without parents. Nests with artificial clutches have a higher morality than natural nests. Clutch size fails to affect the nest predation rates for natural nests. Nest characteristics such as detectability affect the nest failure rates in the absence of parents, but not in their presence.

Wintering redshanks (Tringa totanus) in an estuary in Scotland were examined for anti-predator patterns and an extremely high mortality rate resulting almost exclusively from predation by raptors. The presence of sparrowhawks (Accipiter nisus) causes a small flock to fly, but bigger flocks were selectively assaulted.

A study of redshank Tringa totanus alarm calls suggests that the process accords with the flock recruitment hypothesis, since the calls are predominantly directed at conspecifics. The calling frequency increases in habitats featuring visual obstructions. The bird chased by a sparrow hawk calls frequently to draw enough numbers to confuse the chaser.

Field studies show that in redshanks, Tringa totanus, escape responses to predation depend on the species of predator and the type of attack. Redshanks in East Lothian, Scotland, that are subject to frequent raptor attacks, were studied. Attacks were made by sparrowhawks, peregrines and merlins and were classified as surprise, non-surprise or stoop attacks. Redshank responses were classified on the position of the attacked bird on escape or capture as crouching, creek dive or flying. Escape responses for one raptor species often led to capture in a different species.

The link between the foraging rates and the body masses of wintering European blackbirds is studied. Individuals with the lowest foraging rates had the largest gain in mass for the winter and had relatively high mass overall, independent of age and sex.

Coral reefs are in decline worldwide. While coral reef managers are limited in their ability to tackle global challenges, such as ocean warming, managing local threats can increase the resilience of coral reefs to these global threats. One such local threat is high sediment inputs to coastal waters due to terrestrial over-grazing. Increases in terrestrial sediment input into coral reefs are associated with increased coral mortality, reduced growth rates, and changes in species composition, as well as alterations to fish communities. We used general linear models to investigate the link between vegetation ground cover and tree biomass index, within a dry-forest ecosystem, to coral cover, fish communities and visibility in the case study site of Bonaire, Caribbean Netherlands. We found a positive relationship between ground cover and coral cover below 10 m depth, and a negative relationship between tree biomass index and coral cover below 10 m. Greater ground cover is associated to sediment anchored through root systems, and higher surface complexity, slowing water flow, which would otherwise transport sediment. The negative relationship between tree biomass index and coral cover is unexpected, and may be a result of the deep roots associated with dry-forest trees, due to limited availability of water, which therefore do not anchor surface sediment, or contribute to surface complexity. Our analysis provides evidence that coral reef managers could improve reef health through engaging in terrestrial ecosystem protection, for example by taking steps to reduce grazing pressures, or in restoring degraded forest ecosystems. [ABSTRACT FROM AUTHOR]

Research describing blackbird feeding patch choice decisions is presented. It is shown that blackbirds are not influenced in their choice of patch by the behavior of other blackbirds.

Abstract: Nest predation accounts for a substantial share of nest failure and low reproductive success in most tropical songbirds. Normally, forest fragmentation leads to an increase in nest predation pressure due to reduced cover, fewer (and poorer) nest sites and predator influxes from the surrounding habitats. To test this hypothesis, we studied natural nesting behaviour and nest success of the white-starred robin (Pogonocichla stellata) in seven Afrotropical forest fragments differing in size and level of habitat disturbance. Based on data from 12 nests, we estimate that 29% of all natural nests initiated by the robins survive to produce fledglings across all fragments. We also conducted an experiment using artificial (plasticine) model-eggs to reveal potential predators and compare relative predation rates amongst fragments. This experiment revealed that small mammals might be the major predators on robin nests at the egg-stage. In addition, it showed that the highest incidences of nest disturbance during this stage were in the most heavily disturbed fragment. This was presumably attributable to an influx of mammalian predators from the surrounding habitats as forest degradation created suitable habitats for them. Such an infiltration was recently reported in this study site. Both nest placement and microhabitat did not significantly affect depredation levels in our experiment. This suggests that depredation was predominantly incidental (i.e., predators mainly encountered nests fortuitously while foraging for other food items), where the likelihood of encountering a nest largely depended upon the prevalence of the principal potential predators – the small mammals. [Copyright &y& Elsevier]