Factors Affecting Egg Predation by American Crows

Sullivan, Brian D.; Dinsmore, James J.

doi:10.2307/3809654

Cited by 41 publications

(25 citation statements)

References 11 publications

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“…Alternatively, predation efficiency may decrease over the season (e.g. due to increasing vegetation cover, Sullivan and Dinsmore ), which may encourage the emergence and persistence of mixed strategies, similar to the bimodal pattern predicted by the simulation model.…”

Section: Discussionmentioning

confidence: 63%

Predation can select for later and more synchronous arrival times in migrating species

Harts

Kristensen

2016

Oikos

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For migratory species, the timing of arrival at breeding grounds is an important determinant of fitness. Too early arrival at the breeding ground is associated with various costs, and we focus on one understudied cost: that migrants can experience a higher risk of predation if arriving earlier than the bulk of the breeding population. We show, using both a semi-analytic and simulation model, that predation can select for later arrival. This is because of safety in numbers: predation risk becomes diluted if many other individuals, either con-or heterospecific, are already residing in the area. Predation risk dilution can also select for more synchronous arrival because deviating from the current population-wide norm to earlier or later dates leads to higher predation risk or to failures in territory acquisition, respectively. The fact that selection for high arrival synchrony can in some cases be more important than selection for a specific date (early or late) within the season is an example of an 'evolutionary priority effect': whichever strategy -in this case a particular arrival time -becomes established in a population can remain stable over long periods of time; there are many possible equilibria (multiple stable states) which the population can remain at. Mixed arrival strategies are also possible under some circumstances.

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Section: Discussionmentioning

confidence: 63%

Predation can select for later and more synchronous arrival times in migrating species

Harts

Kristensen

2016

Oikos

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“…Several studies have shown that predation on ground‐nesting bird nests by avian predators tends to decrease during the season, possibly because of the increasing vegetation height and density (Hill 1984, Beintema and Müskens 1987, Johnson et al 1989). I did not detect any significant changes in predation rates between the early and late breeding period (see Material and methods), presumably because vegetation growth was insufficient to reduce harrier predation rates, as found in American crows Corvus brachyrhynchos (Sullivan and Dinsmore 1990). Similarly, harrier nest finding rates did not change in different weather conditions.…”

Section: Discussionmentioning

confidence: 79%

Appearance and vulnerability of artificial duck nests to avian predators

Opermanis¹

2004

Journal of Avian Biology

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Use of artificial nests in studies of nest success in birds has become increasingly popular, but this practice has been criticised because the appearance and success of artificial nests may differ from natural nests. Typically, artificial nests are presented with few visible eggs throughout the entire exposure period while natural nests during their life have different appearances, possibly producing stage‐dependent predation rates. In ducks, nests may appear with openly visible eggs, eggs covered with nest material and covered by an incubating female. To test how nest appearance may affect nest survival, I simulated such duck nest appearances, and used direct observations to record responses of marsh harriers Circus aeruginosus, the dominant duck nest predator at the Lake Engure, Latvia, during the breeding seasons 2000–2002. I recorded 274 harrier flights over all types of artificial nests, 74 nest discoveries and 54 predation events. Logistic regression analyses showed that nest appearance was a significant predictor of the fate of the nest: nests with openly visible eggs were discovered more often than nests covered with nest material. Nests with dummy females had discovery rates similar to the average of all artificial nest types suggesting that they best reflect the predation risk of artificial nests and could be used in future studies. After discovering nests covered with dummy females, harriers never attacked but tried to scare them off to get access to the eggs. In 52% of cases of nest discovery, harriers gave up before touching the dummy. This shows that duck passive nest defence may prevent clutch predation.

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“…Higher duck nest densities are generally observed close to gull colonies (Koskimies 1957;Hilden 1965;Dwernychug and Boag 1972) where nest predation may be lower (Bengtson 1972;Newton and Campbell 1975;Young and (Sullivan and Dinsmore 1990;Albrecht et al 2006). This result is in accordance with the specific habitat use of Pochard in fishpond regions (Havlin 1966).…”

Section: Discussionmentioning

confidence: 96%

“…Purple Heron is an indicator species of reedbeds that are flooded during the waterfowl breeding period, without sudden water level variations (Moser 1984;Broyer et al 1998). Such reedbeds may provide adequate vegetation cover to the duck species that tend to nest above water to limit the risk of clutch predation (Nice 1957;Sullivan and Dinsmore 1990).…”

Section: Introductionmentioning

confidence: 99%

Compared distribution within a disturbed fishpond ecosystem of breeding ducks and bird species indicators of habitat quality

Broyer

2009

J Ornithol

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The distribution of breeding ducks versus three other bird species (Mute Swan Cygnus olor, Black-headed Gull Larus ridibundus and Purple Heron Ardea purpurea) among waterbodies was investigated in the Dombes area, Eastern France, where breeding duck populations have undergone a severe decline following a large-scale transformation of meadow habitat into cropland. Higher Pochard Aythya ferina, Tufted Duck Aythya fuligula, Redcrested Pochard Netta rufina and Gadwall Anas strepera pair densities were recorded in fishponds where Blackheaded Gulls were nesting. In these ponds however, nesting success (assessed by the number of broods divided by the number of pairs) was not significantly higher. Similarly, Pochard pair density was higher in ponds with a Purple Heron colony, but brood densities were not. We hypothesise that, in the study region, clutch concentration in the most attractive areas could compensate for the anti-predation effect of gull colonies or overwater nesting in shore vegetation. We could not confirm the expected negative impact of Mute Swan aggressive behaviour on duck distribution. Even though Mallard Anas platyrhynchos pair density was lower in ponds with breeding swans, we did not observe difference for Mallard broods. Moreover, Redcrested Pochard pair density and nesting success were higher in ponds where swans were breeding, probably as a consequence of shared habitat preferences.

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Factors Affecting Egg Predation by American Crows

Cited by 41 publications

References 11 publications

Predation can select for later and more synchronous arrival times in migrating species

Predation can select for later and more synchronous arrival times in migrating species

Appearance and vulnerability of artificial duck nests to avian predators

Compared distribution within a disturbed fishpond ecosystem of breeding ducks and bird species indicators of habitat quality

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