Patterns of Nest Predation on Artificial and Natural Nests in Forests

Abstract

Artificial nest experiments have been used in an attempt to understand patterns of predation affecting natural nests. A growing body of literature suggests that neither relative rates nor patterns of predation are the same for artificial and natural nests. We studied nest predation and daily mortality rates and patterns at real and artificial ground and shrub nests to test the validity of artificial nest experiments. We monitored 1667 artificial and 344 natural nests, over seven trials, in three regions, across 58 sites in Ontario. We controlled for many of the factors thought to be responsible for previously reported differences between predation rates on natural and artificial nests. Although artificial nests in our study resembled natural nests, contained eggs of appropriate size, shape, and color of target bird species, and were placed in similar microhabitats as natural nests, the rates of predation on these nests did not parallel rates on natural nests for any region in terms of absolute rate or pattern. Predation rates on artificial nests did not vary between years, as they tended to for natural nests, and the magnitude of predation pressure on artificial ground nests compared with shrub nests did not show the same pattern as that on natural nests. In general, rates of predation on artificial nests were significantly higher than on natural nests. Our results suggest that conclusions derived from artificial nest studies may be unfounded. Given that many influential ideas in predation theory are based on results of artificial nest experiments, it may be time to redo these experiments with natural nests.Resumen: Se han utilizado experimentos con nidos artificiales con la intención de entender los patrones de depredación que afectan a los nidos naturales. La bibliografía sugiere que ni las tasas relativas ni los patrones de depredación son iguales para nidos artificiales y naturales. Estudiamos las tasas y patrones de depredación de nidos y de mortalidad diaria en nidos reales y artificiales sobre el suelo y en matorrales para probar la validez de los experimentos con nidos artificiales. Monitoreamos 1667 nidos artificiales y 344 nidos naturales, en siete pruebas, en tres regiones, en 58 sitios en Notario. Controlamos muchos de los factores que se piensa son responsables de diferencias entre tasas de depredación en nidos naturales y artificiales reportadas previamente. Aunque los nidos artificiales en nuestro estudio se asemejaron a nidos naturales, contenían huevos de tamaño, forma y color adecuados para la especie de ave y fueron colocados en microhábitats 382 Predation Patterns on Artificial and Real NestsBurke et al.similares a los de nidos naturales, las tasas de depredación en estos nidos no fueron similares a las tasas en nidos naturales en ninguna región en términos de tasa o patrón absoluto. Las tasas de depredación en nidos artificiales no variaron de un año a otro, como fue la tendencia en nidos naturales, y la magnitud de la presión de depredación en nidos sobre el suelo comparada con nidos en arbu...

Predation on artificial nests in open habitats of central Brazil: effects of time and egg size

“…Similar results have been reported for temperate (Maier & DeGraaf 2000, Coppedge et al 2007) and neotropical forests (Alvarez & Galetti 2007). Comparisons between artificial and natural nests also revealed the importance of controlling egg size (Roper 2003, Berry & Lill 2003, Burke et al 2004, Robinson et al 2005. The importance of other characteristics such as egg color and scent seems marginal (review in Major & Kendal 1996).…”

“…The tested hypotheses were: (1) predation on artificial nests with large eggs will be less than that on nests with small eggs (Roper 1992, Alvarez & Galleti 2007; (2) the risk of predation will increase over time during the reproductive season, as observed in some studies with natural nests in neotropical areas (Borges & Marini 2010, Duca & Marini 2005; (3) predation risk will be greater in shrubs habitat than in trees, because predation tends to be greater in savanna than in forest (see Duca (Dinsmore et al 2002), and to sort candidate models based on Akaike Information Criterion adjusted for small samples (AIC c ; Burnham & Anderson 1998). The best-fit model was the one with the lowest AIC c value and models with ∆AIC c ≤ 2 were considered to have substantial support to explain variation in the data (Burnham & Anderson 1998). We used the daily nest survival of the best-fit model to estimate nest success based on 15 days of incubation.…”

Population demography of Gray Catbirds in the suburban matrix: sources, sinks and domestic cats

“…At each nest visit, we recorded the number of eggs and nestlings. Nests that produced at least one fledgling were categorized as successful, otherwise as failed (Burke et al 2004). On the eighth or ninth day of the nestling stage, all nestlings were banded using USFW aluminum bands and weighed to the nearest 0.1 g using a digital scale.…”

Using artificial nests to explore predation by introduced predators inhabiting alpine areas in New Zealand

“…Artificial nest experiments are commonly used overseas to study nest survival (henry 1969;yahner & Wright 1985;Major 1991). however, their use has been criticised for a number of reasons: (1) Artificial nest survival is often a poor predictor of reproductive success in real bird populations (Major & kendal 1996;Batary & Baldi 2004;Burke et al 2004;Faaborg 2004;Thompson & Burhans 2004), in part because artificial nests do not realistically represent real nests, and in part because nest survival is not always correlated with fledgling survival (e. C. Murphy unpubl. data).…”