Racketed Tail of the Male and Female Turquoise-Browed Motmot: Male but Not Female Tail Length Correlates with Pairing Success, Performance, and Reproductive Success

Both males and females of many avian species maintain elaborate plumage traits, and elaborate monomorphic plumage may convey adaptive benefits to one or both sexes as inter- or intraspecific signals. Both sexes of the turquoise-browed motmot (Eumomota superciliosa) are elaborately plumed with long racket-tipped tail. I investigated whether the racketed tail functions as a sexually selected signal in one or both sexes by testing the predictions that males and/or females with the largest tails have: (1) greater pairing success, (2) greater reproductive performance (clutch-initiation date, clutch size, and hatching success), and (3) greater reproductive success. Yearling males with longer denuded rachises (wires) on the central tail feathers had greater pairing success. In addition, adult males with longer wires paired with females who laid larger clutches, had greater hatching success independent of clutch size, and fledged more young. There was no relationship between female tail plumage and pairing success, reproductive performance, or fledgling success. These results are consistent with the hypothesis that male tail plumage functions as a mate choice or status signal, but that the tail of the female does not function in a sexually selected context. I discuss alternative hypotheses for the evolutionary maintenance of the elaborate female tail plumage

Display of an Inedible Prop as a Signal of Aggression? Adaptive Significance of Leaf-Display by the Turquoise-Browed Motmot, \u3cem\u3eEumomota superciliosa\u3c/em\u3e

The incorporation of an inedible object (prop) into a behavioral display is rare among birds. Only four avian taxa have been reported to display with a prop, and in all studied species, prop use has been found to play a role in mate acquisition. However, little is known about the context and adaptive significance of prop use by the motmots. Both male and female motmots perform a leaf-display, whereby a leaf is held horizontally in the tip of the bill for an extended period. I collected observational data on leaf-display by the turquoise-browed motmots (Eumomota superciliosa) to investigate the potential role of this display as a mate-choice or agonistic signal. Observations of 61 leaf-displays by 27 individuals indicate that males and females are similarly likely to perform the leaf-display, that the leaf-display is performed throughout the long-breeding season, and that the display is performed by both paired and unpaired birds. These observations suggest that the leaf-display does not play a role in mate-attraction. However, the leaf-display was often performed in association with a chase or fight with a same-sex individual, and the display was sometimes performed in conjunction with an agonistic display at nest sites, suggesting that the leaf-display may function in both sexes as a signal of aggressive intent or as a signal of status

Dishonest ‘Preemptive’ Pursuit-Deterrent Signal? Why the Turquoise-Browed Motmot Wags Its Tail Before Feeding Nestlings

Both sexes of the turquoise-browed motmot, Eumomota superciliosa, display their long-racketed tail in an exaggerated side-to-side wag display in two contexts. In the first, the wag display is performed in the presence of predators (predator-elicited wag display), and evidence supports the hypothesis that the signal functions as a pursuit-deterrent signal (Murphy 2006, Behavioral Ecology, 17, 547e553). In the second, the wag display is performed in the apparent absence of predators immediately before feeding nestlings (prefeeding wag display). I tested four hypotheses on the adaptive significance of the prefeeding wag display: (1) a dishonest, preemptive, pursuit-deterrent signal given in case predators are present; (2) a nonfunctional misfire of the predator-elicited wag display; (3) a signal that alerts nestlings to the delivery of food; (4) a sexually selected signal that advertises parental quality to potential mates. There was no support for the hypotheses that the prefeeding wag display was directed to nestlings or potential mates. The wag display was generally performed where nestlings could not detect the signal and the display did not vary with the sex of the displaying bird, the presence of the mate, or the size of the food carried in the signaller’s bill. Evidence presented in this paper is most consistent with the hypothesis that the predator-elicited wag display and the prefeeding wag display are performed as a response to the presence or the potential presence of a predator. I discuss the possibility that the prefeeding wag display functions as a dishonest, pursuit-deterrent signal

Predator-Elicited Visual Signal: Why the Turquoise-Browed Motmot Wag-Displays Its Racketed Tail

Both sexes of the turquoise-browed motmot (Eumomota superciliosa) perform a wag-display in the presence of predators, whereby their long racketed tail is repeatedly rocked side-to-side in a pendulous fashion. I tested 3 hypotheses for the function of the predator-elicited wag-display: 1) pursuit-deterrent signal, 2) warning alarm signal, and 3) self-preservation alarm signal. These hypotheses were evaluated by testing whether the presence of potential receivers (kin, conspecifics, mate) modified the way in which the wag-display was performed. Data on wag-display were collected when I experimentally presented predators to motmots and when naturally occurring predators were observed at nesting colonies. The wag-display was performed by male and female motmots who were 1) alone and not within signaling distance of conspecifics, 2) unpaired and therefore not signaling to a mate, and 3) paired but away from their mate. Motmots in these contexts performed the wag-display with similar probability and in a similar manner as individuals that were within signaling distance of conspecifics, paired birds, and paired birds who were near their mate. These results support the hypothesis that the predator-elicited wag-display is directed to the predator and functions as a pursuit-deterrent signal

Seasonal Variation in the Utility of a Status Signaling System: Plumage Ornament Predicts Foraging Success Only During Periods of High Competition

Status signals allow competitors to assess each other’s resource holding potential and reduce the occurrence of physical fights. Because status signals function to mediate competition over resources, a change in the strength of competition may affect the utility of a status signaling system. Status signals alter competitor behavior during periods of high competition, and thus determine access to resources; however, when competition is reduced, we expect these signals to become disassociated from access to resources. We investigated seasonal changes in status signaling of the male black-crested titmouse (Baeolophus atricristatus), a species that experiences substantial changes in population density and competition for food over the annual cycle. We compared the size of the prominent head-crest to foraging success at community-used feeding stations; we tested this relationship when competition was seasonally high, and when competition was seasonally low. We then experimentally decreased the number of feeders to increase competition (during the season of low-competition), and again tested whether male crest size predicted access to feeders. When competition was seasonally high, males with longer crests had greater access to feeders, but this pattern was not apparent when competition was seasonally low. When competition was experimentally increased, males with longer crests were again more successful at maintaining access to feeders. These findings provide evidence of a context-dependent status signaling system, where the status signal only mediates access to resources during periods of high competition. We discuss possible hypotheses for why the signaling system may not be functional, or detectable, during periods of low competition, including that competitors may interact less frequently and so have reduced opportunity for signaling, or that status signals are disregarded by receivers during periods of low competition because signalers are unlikely to escalate a contest into a fight. In any case, these results indicate that resource availability affects a status signaling system, and that the potential for status signaling persists in this system between seasons, even though such signaling may not be overtly present or detectable during periods of low competition

Painted Bunting (\u3cem\u3ePasserina ciris\u3c/em\u3e) Caught in the Web of a Giant Lichen Orb-Weaver Spider (\u3cem\u3eAraneus bicentenarius\u3c/em\u3e)

Orb-weaver spiders weave large webs that are capable of entrapping various species of birds. We report a case of a male Painted Bunting (Passerina ciris) caught in the web of a giant lichen orb-weaver (Araneus bicentenarius). Most cases of bird entrapment in spider webs involve spiders with larger webs (often Nephila sp.) and very small birds, usually hummingbirds. Our case is noteworthy because we report a relatively large bird caught in a relatively small web. Furthermore, the geographic distribution of A. bicentenarius extends beyond the tropics and subtropics, which is where most reported cases of bird entrapment occur. This observation suggests that even small orb-weaver webs may pose a threat to relatively large birds, and that this risk may extend well beyond the regions most commonly associated with entrapment

It Isn\u27t Always Sexy When Both are Bright and Shiny: Considering Alternatives to Sexual Selection in Elaborate Monomorphic Species

Since the dawn of abstract thinking, humans have wondered about the seemingly unnecessary elaborate ornamentations of birds. Gaudy colours, cumbersome tails, complex vocalizations and bizarre displays are found in bird species from all corners of the globe. Darwin (1871) provided an elegant explanation for the existence of these non-utilitarian traits: they increase mating success, and although they may impair survival, the costs of producing and bearing elaborate ornaments can be repaid in the currency of additional offspring. Darwin’s model still serves as the foundation for our concept of sexual selection but great strides have been made in our understanding of sexual selection processes since his time (e.g. Zahavi 1975, 1977, Lande 1980, Hamilton & Zuk 1982, Kirkpatrick 1982, Grafen 1990, Andersson 1994). The great majority of work to date has focused on species in which males alone are elaborately ornamented. Far less has been published on the function of ornaments that are expressed in both sexes (Kraaijeveld et al. 2007), a condition sometimes termed ‘elaborate monomorphism.’ As such, the question remains whether the strong generalizations that we make regarding male ornamentation also apply to species in which both sexes are ornamented

Condition and Brightness of Structural Blue-Green: Motmot Tail-Racket Brightness is Related to Speed of Feather Growth in Males, But Not in Females

Coloration plays an important role in sexual and social communication, and in many avian species both males and females maintain elaborate colours. Recent research has provided strong support for the hypothesis that elaborate female traits can be maintained by sexual or social selection; however, most research on female ornamentation has focused on pigment-based colours, and less is known about how structural colours are maintained. Both sexes of the turquoise-browed motmot (Eumomota superciliosa) have a blue-green racket-tipped tail, and it remains unknown if tail coloration serves as a sexual or social signal in one or both sexes. Here, we describe sexual dichromatism in the blue-green portion of the tail racket, and we test for a relationship between coloration and condition, as indicated by growth bars. Tail colour of both sexes has a similar spectral shape, and there is significant, although moderate, sexual dichromatism: males are brighter than females, and males have marginally greater blue-green saturation than females. The length of feather grown per day is positively related to overall feather brightness, but this relationship is only present in males. The relationship between male coloration and condition suggests that tail colour has the potential to convey information about individual quality during mate choice or contest competition. The lack of a similar relationship in females suggests that female tail colour does not convey the same condition-dependent information that we suggest may be reflected by male colour. Female tail colour may therefore reflect other aspects of condition, be involved in other (non-condition-dependent) forms of communication, or be expressed as a non-functional byproduct of genetic correlation between the sexes

Breeding Biology and Longevity of Russet-Crowned Motmots in Central Mexico

Motmots, with their distinctive racketed-tails, represent one of the most easily recognized tropical birds, yet little is known about the basic natural history of most species in the family Momotidae. We report basic breeding biology and longevity of Russet-crowned Motmots (Momotus mexicanus), a medium-sized Neotropical bird that ranges from northwest Mexico to central Guatemala. We monitored nest success of eight pairs from 1 May to 17 July 1998 in tropical deciduous forests in central Mexico. Motmots laid an average of 4.1 eggs and incubated for approximately 20 d. Four of eight nests fledged young. Of these four nests, average hatching success was 69% and average fledgling success was 56%. The mean duration of the nestling period at three nests was 33.7 d. Based on the recapture of one individual bird in April 2008, we provide a longevity estimate that Russet-crowned Motmots can survive at least 11 yr in the wild. These data on nesting success and longevity add to our limited knowledge of the natural history of this understudied species

Colorful Displays Signal Male Quality in a Tropical Anole Lizard

Parasites influence colorful ornaments and their behavioral display in many animal hosts. Because coloration and display behavior are often critical components of communication, variation in these traits may have important implications for individual fitness, yet it remains unclear whether such traits are signals of quality in many taxa. We investigated the association between ectoparasitic mite load and the color and behavioral use of the throat fan (dewlap) by male Anolis brevirostris lizards. We found that heavily parasitized lizards exhibited lower body condition, duller dewlaps, and less frequent dewlap displays than less parasitized individuals. Our results thus suggest that highly parasitized individuals invest less in both ornamental color and behavioral display of that color. Because the two components of the signal simultaneously provide information on male quality, this study provides novel support for the long-standing hypothesis that colorful traits may function as social or sexual signals in reptiles