Probing parentage in parasitic birds: an evaluation of methods to detect conspecific brood parasitism using goldeneyesBucephala islandicaandBl. clangulaas a test case

Abstract

Conspecific brood parasitism (CBP) occurs in over 200 species of birds. Efforts to detect CBP have relied on either observational criteria, or more recently, on molecular methods. While molecular approaches are powerful, they are expensive, time consuming and may prove prohibitive for studies requiring estimates of CBP over large spatial and temporal scales involving hundreds of nests. We evaluated a series of observational methods that have been applied in previous studies to detect CBP, using two species of cavity-nesting ducks, the Barrow's goldeneye Bucephala islandica and common goldeneye B. clangula, as test species. We first describe a method based on differences in egg morphology and find it to be a reliable method to detect CBP in both species in British Columbia, Canada. The application of recursive partitioning analysis was especially effective in classifying parasitized and non-parasitized nests using differences in egg morphology. We then evaluated five additional observational criteria that have been used previously in several studies to detect CBP in birds. We show that considerable redundancy exists among all criteria, as expected, but no single method is effective at detecting all suspected cases of CBP. Subsets of criteria (2 or more eggs/d, eggs laid 2 or more days after incubation, and clutch sizes exceeding 12 eggs) were successful, in combination, in detecting 75% of parasitized nests for goldeneyes. Finally, we suggest that ecological and evolutionary analyses of the dynamics of CBP will require estimates of the frequency of the parasitic tactic in the population (rather than just the proportion of parasitized nests) and we provide a simple method to obtain such an estimate. Although our data are specific to goldeneyes, the techniques we used should have broad application to other studies of CBP.

Linking nest predation with brood parasitism in captive zebra finches: a multi-pair study

“…In the absence of genetic analyses of the putatively parasitic eggs laid in our study, alternative explanations for the patterns of egg laying detected in our experimental treatment, which do not invoke parasitism by the focal females, cannot be entirely ruled out (Latif et al 2006;Eadie et al 2010). However, given the apparent absence of Trials where there was evidence of parasitism in the group following the manipulation are marked Y; trials in which there was no evidence of parasitism are marked N d Females in these pairs did not lay eggs the day following the manipulation, but after this single-day delay, a parasitic egg did appear in the aviary e The female in this pair was seen attempting to enter a neighbouring nest and being chased away by the nest-occupiers the morning following the manipulation, before laying her egg from the perch any putative evidence of brood parasitism in control trials (as indicated by the lack of supernumerary eggs in any of the active nests or the presence of new eggs in the simulated nests), it remains reasonable to infer that parasitism took place following the removal of a female's nest when eggs appeared in simulated active nests, or when more than one egg was laid in a real active nest in the 24 h following the experimental manipulation.…”

Brood parasitism, relatedness and sociality: a kinship role in female reproductive tactics

“…Before molecular‐genetic methods became available, CBP was often inferred by larger than normal clutch size, addition of more than one egg per day, addition after incubation start, and differences in egg size, shape and colour (reviewed by Eadie & Savard, ). Such methods have limited detection power: in goldeneyes, three of these criteria together identified 75% of parasitized nests (Eadie et al ., ). Combination of more than one egg added per day, or a clutch exceeding 12 eggs, in goldeneyes detected less than half of the parasitic eggs found by protein fingerprinting (Andersson & Åhlund, ).…”

Alloparental care in the sea: Brood parasitism and adoption within and between two species of coral reef Altrichthys damselfish?

“…The large frequency of conspecific mixed broods is also consistent with the observation that there is a significant relationship between mixed broods and brood size, since adoption and parasitism directly contribute to brood size. In avian studies, this same relationship between clutch size and parasitism has been observed and has been used as a method for detecting brood parasitism (Eadie, Smith, Zadworny, Kühnlein, & Cheng, ).…”