Vocal Response of Eared Grebe Embryos to Egg Cooling and Egg Turning

Abstract

AI•STRACT.-In a laboratory study, the vocal responses of Eared Grebe (Podiceps nigricollis) embryos to egg cooling and egg turning were examined. Nineteen late-stage, prepipping embryos were twice subjected to 10 min of egg cooling and 10 min of normal incubation temperatures. Experimentally cooled embryos vocalized more than embryos exposed to normal incubation temperatures. Cooled embryos produced more bouts of calls and fewer calls per bout than when exposed to normal incubation temperatures. Intercall intervals within bouts did not differ between warm and cold periods. Results of the egg-cooling experiment support the "care-soliciting signal" hypothesis. In a separate paired experiment, embryos vocalized more when turned than when at rest. Because grebe nests are composed of sodden materials, embryos that are about to hatch may signal their parents to turn the eggs, because positioning a pipped egg upside down may suffocate the embryo. Also, prepipped embryos may vocalize more frequently when turned as a signal to their parents that they are viable and will soon hatch. Eared Grebe embryonic vocalizations probably are multifunctional, with care-soliciting being one of their functions.

Plasticity in incubation behavior and shading by king rails Rallus elegans in response to temperature

“…In species more tolerant of extreme temperatures, embryos may be able to partially regulate their own temperature, or to control their exposure to heat behaviorally to some extent by moving within the egg to avoid hotspots (Du and Shine ). More developed embryos make sounds, likely prompting more attentive behavior from the parents (Bugden and Evans , Brua et al ). Heat shock proteins, a subset of molecular chaperones that help organisms cope with thermal stress (Sørensen et al ), may play an important role in embryo heat tolerance, but this is largely unstudied in birds (Du and Shine ).…”

Perinatal Acoustic Communication in Birds: Why Do Birds Vocalize in the Egg?

“…This facultative acoustic reaction to embryonic calls was also characteristic for the Pekin duck [22] and for the Oystercatcher (Haematopus ostralegus L.) [68]. Although the breeding parent of the Eared Grebe (Podiceps nigricollis Brehm) does not vocalize in response to the embryos vocalization [69], embryonic vocalizations may alter the parental behaviour [69]. In others species too, vocalizations of the embryos may affect the behaviour of the parent [25,[70][71][72] for instance egg-turning, nest building or the amount of time parents spend on the nest, manipulating the nest and nictitating or alteration of egg-turning angle [pers.…”

“…It is well known, that the young of many bird species emit distress calls and induce maternal brooding in order to be warmed. Bird embryos such as Muscovy ducks, Eared Grebes or White Pelicans also react to cooling with higher rate of distress calling [69,77,78]. It seems to depend on the species and its ecological needs whether distress calls change parental behaviour or not.…”

Prolonged incubation of unhatchable eggs in Red-necked Grebes (Podiceps grisegena)

“…Although causes of nonviability were not determined for all eggs, it is unlikely that any of them peeped, which begins 1-3 days before hatching (McAllister 1963). Prolonged attendance of inviable eggs in nests with at least one hatched young is remarkable in the light of the recent interpretations of embryonic vocalizations as care soliciting signals, which, among other functions, prevent parental neglect after the onset of hatching (Evans 1988;Brua et al 1996).…”