Which egg features predict egg rejection responses in American robins? Replicating Rothstein's (1982) study

Abstract

Rothstein (Behavioral Ecology and Sociobiology, 11, 1982, 229) was one of the first comprehensive studies to examine how different egg features influence egg rejection behaviors of avian brood parasite–hosts. The methods and conclusions of Rothstein (1982) laid the foundation for subsequent experimental brood parasitism studies over the past thirty years, but its results have never been evaluated with replication. Here, we partially replicated Rothstein's (1982) experiments using parallel artificial model egg treatments to simulate cowbird (Molothrus ater) parasitism in American robin (Turdus migratorius) nests. We compared our data with those of Rothstein (1982) and confirmed most of its original findings: (1) robins reject model eggs that differ from the appearance of a natural robin egg toward that of a natural cowbird egg in background color, size, and maculation; (2) rejection responses were best predicted by model egg background color; and (3) model eggs differing by two or more features from natural robin eggs were more likely to be rejected than model eggs differing by one feature alone. In contrast with Rothstein's (1982) conclusion that American robin egg recognition is not specifically tuned toward rejection of brown‐headed cowbird eggs, we argue that our results and those of other recent studies of robin egg rejection suggest a discrimination bias toward rejection of cowbird eggs. Future work on egg recognition will benefit from utilizing a range of model eggs varying continuously in background color, maculation patterning, and size in combination with avian visual modeling, rather than using model eggs which vary only discretely.

Contrasting effects of egg size and appearance on egg recognition and rejection response by Oriental reed warblers

“…This experiment was further replicated by Luro et al. (2018), which confirmed most of the original findings, but also showed that variation in egg size was less predictive than the other two features. Guigueno et al.…”

“…(2006) and Luro et al. (2018) that for an egg rejecter host, egg size has relatively less effect than other visual traits of the eggshell.…”

Self‐referent phenotype matching is a poor predictor of egg rejection by American Robins

“…This includes the individually repeatable eggshell coloration of female American Robins ( Turdus migratorius ), an occasional host of obligate brood‐parasitic Brown‐headed Cowbirds ( Molothrus ater ; Croston and Hauber 2015). American Robins have been the subject of many classic and recent parasitic egg‐rejection studies (e.g., Friedmann 1929, Rothstein 1982, Briskie et al 1992, Rasmussen et al 2009, Lang et al 2014, Abernathy and Peer 2015, Igic et al 2015, Carmody et al 2016, Luro and Hauber 2017, Luro et al 2018).…”

Egg recognition in Cinereous Tits (Parus cinereus): eggshell spots matter

“…(1) egg spots do not contribute to egg recognition, and egg size is the main clue to identifying eggs (Mason and Rothstein 1986;Marchetti 2000;Langmore et al 2003); (2) spot patterns and egg colors are more important than egg size for egg recognition (Rothstein 1978;Lawes and Kirkman 1996;Igic et al 2015;Antonov et al 2006); (3) both egg colors and spot patterns affect egg rejection behavior by the host, but the egg colors are more important than the spot patterns (Lahti and Lahti 2002;Spottiswoode and Stevens 2010;Luro et al 2018); (4) egg spot patterns are more important than egg colors for egg recognition (Underwood and Sealy 2006;López-De-Hierro and Moreno-Rueda 2009;de la Colina et al 2012;Šulc et al 2016); and (5) spots on the blunt pole of the egg provide a cue for egg recognition (Lahti and Lahti 2002;Polačiková et al 2007Polačiková and Grim 2010). There were so many different signals influencing the host's response.…”