Do Field Observers Attract Nest Predators and Influence Nesting Success of Common Eiders?

Götmark, Frank; Åhlund, Matti

doi:10.2307/3801169

Cited by 68 publications

(34 citation statements)

References 11 publications

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“…Other egg predators were raven Corvus corax, arctic skua Stercorarius parasiticus and polar bear Ursus arctos (also see Schmutz et al 1983). To avoid increasing the risk of predation we always covered the clutch with debris or down after handling (Go¨tmark and Å hlund 1984), and so did most females when leaving the nest. Conspecific brood parasitism is common in this population, and an estimated 20-42% of the nests were parasitised in studies by Robertson (1998) and Waldeck and Andersson (2006).…”

Section: Methodsmentioning

confidence: 99%

Reproductive tactics under severe egg predation: an eider’s dilemma

Andersson

Waldeck

2006

Oecologia

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Parental defence against predators may increase offspring survival but entail other costs. Egg predation is frequent early in the laying sequence of the common eider, which differs in this and in several other ways from most other waterfowl. We test the hypothesis that permanent presence at the nest from the second or third egg is an adaptation for reducing egg predation in eiders. Two other alternative hypotheses for lower predation at later nest stages are early predation loss of the most vulnerable nests and seasonal decrease in predation risk. Analyses of predation rates at the one-egg and later stages refute these two alternatives. Early nest attendance by eider females is estimated to increase clutch survival by about 20% in four-egg and 35% in five-egg clutches, albeit probably at a cost of smaller clutch size.

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Section: Methodsmentioning

confidence: 99%

Reproductive tactics under severe egg predation: an eider’s dilemma

Andersson

Waldeck

2006

Oecologia

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“…In addition, the closure of the in-shore fishery likely resulted in less disturbance of breeding colonies (Gotmark and Ahlund 1984; by fishing boats, as well as possible reductions in egging and the harvest of adult birds.…”

Section: Discussionmentioning

confidence: 99%

Suspected Long-Term Population Increases in Common Eiders, <em>Somateria mollissima</em>, on the Mid-Labrador Coast, 1980, 1994, and 2006

Chaulk

2009

Can Field Nat

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Aerial surveys for adult male Common Eiders, Somateria mollissima, were flown on the Labrador coast during June 2006. This information was then compared with aerial counts of adult male Common Eiders collected in 1980 and 1994. For each survey year, data were grouped and paired by coastal block and were analyzed for population trends. Overall, the observed counts of adult male Common Eiders increased by 244% between 1980 and 2006. Much of this increase seemed to occur in the southern region of the study area.

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“…Observations may be conducted directly in the field by the observer, or may be carried out with the aid of a video recording system. Several studies indicate that the presence of humans during direct observations can affect the behaviour of the animals (Götmark and Ahlund, 1984;Davis and Balfour, 1992). This problem may be overcome by using video recording systems.…”

Section: Introductionmentioning

confidence: 99%

Comparison of video and direct observation methods for measuring oral behaviour in veal calves

Tosi

Ferrante

Mattiello

et al. 2006

Italian Journal of Animal Science

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Measuring behaviour, especially oral behaviour, has always been a debated issue: therefore the aim of this paper is to closely examine the study of oral behaviour in calves and the approaching methodology. Behavioural observations were conducted by two media (direct observations by check sheets and indirect observations by videotapes recorded by cameras connected to a digital field switcher and a time-lapse video recorder) in order to compare data and assess the reliability and validity of the two methods in identifying some oral behavioural patterns in calves. The study was carried out on 54 Polish Friesian calves housed in group pens and in individual crates. The behaviour of the calves was investigated during the fattening period on the 2 nd , 7 th , 13 th , 18 th and 23 rd week, one hour before and one hour after each of the two meals. Two experienced observers checked the behaviour of the calves, including oral behaviours on structures and buckets and oral stereotypies, by direct observations using a scan sampling every 2 minutes. The calves' behaviour was also video recorded on the same days in which the direct observations were carried out and analysed by the same two observers. Percentages of time spent on each type of behaviour were calculated and analysed by Chi-square test. Regardless of the housing system, the comparison between direct and indirect observations revealed significant differences in almost every behavioural category. Licking, biting and nibbling structures, nibbling and sucking the bucket, playing with the bucket and the teat, chewing and oral stereotypies were significantly higher in direct observations compared to indirect (P < 0.001), while inactivity was higher in video recorded observations (P < 0.001).In conclusion, regardless of the type of housing, our results revealed an objective difficulty in analysing videotapes with very detailed behavioural categories, like oral behaviours. Although video recording can certainly represent a useful and practical alternative to direct observations in many situations, the video recording system used in this study for investigating calves' oral behaviour, in spite of the use of multiple cameras, could not replace direct observations, probably due to the restricted field of view, the low depth of focus, the black and white vision, the lack of audio and the time-lapse feature.

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Do Field Observers Attract Nest Predators and Influence Nesting Success of Common Eiders?

Cited by 68 publications

References 11 publications

Reproductive tactics under severe egg predation: an eider’s dilemma

Reproductive tactics under severe egg predation: an eider’s dilemma

Suspected Long-Term Population Increases in Common Eiders, <em>Somateria mollissima</em>, on the Mid-Labrador Coast, 1980, 1994, and 2006

Comparison of video and direct observation methods for measuring oral behaviour in veal calves

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