Postnatal cranial ontogeny and growth strategies in the black‐tailed gull Larus crassirostris breeding on Kabu Island, Aomori, Japan. (28th June 2021)

• Record Type: Journal Article
• Authors: Hanai, T.; Iwami, Y.; Tomita, N.; Tsuihiji, T.
• Is Part Of: Journal of zoology. Volume 315:Number 3(2021)
• Page Start: 183
• Page End: 198
• Publication Date: 2021-06-28
• Subjects: developmental biology -- allometry -- cranial morphology -- feeding ecology -- sibling competition -- Laridae -- dinosaur paleontology; Zoology -- Periodicals; Zoologie -- Périodiques; 590.5
• DOI: 10.1111/jzo.12907
• Languages: English
• ISSNs: 0952-8369

Abstract

Abstract: Although cranial morphology of modern birds has been an important subject of evolutionary studies, detailed information on postnatal ontogeny of the avian skull remains very scarce. Herein, a wild population of the black‐tailed gull ( Larus crassirostris ) breeding on Kabu Island was examined to explore relationships between their growth strategies and ontogenetic changes in the cranial shape. By examining growth series covering a major part of the postnatal ontogenetic period, it was clarified that the typical form of the adult larid skull was produced through dynamic proportional changes among cranial structures after hatching. Cranial structures related to the oral capacity and deglutition (e.g., some elements of hyoid bones) attained the adult sizes before fledging, whereas other structures apparently reached the adult sizes well after leaving the nest. The palatal width exhibited positively allometric growth against the skull volume in chicks in the early nestling stage, followed by a period of negative allometry in the later growth stage. A nestling gull has to acquire swallowing ability by the time of fledging at the latest because this ability is apparently essential for a food intake without parental aid. In addition, because nestlings mainly feed on foodstuffs supplied by their parents, previous studies suggested the possibility that siblings within a nest compete for food resources. Under this scenario, early acquisition of swallowing abilities, as indicated by the allometric patterns of relevant cranial structures, may be an adaptive trait that enhances survival of nestlings. Abstract : We found a new example that suggests the parallelism between cranial growth allometry and dietary ecology of young birds. Herein, postnatal cranial development of the black‐tailed gull ( Larus crassirostris ) was examined by using images of X‐ray CT scanning. Cranial structures related to the oral capacity and deglutition attained the adult sizes before fledging, whereas other structures apparently reached the adult sizes well after leaving the nest. This development pattern appears to be adaptive and probably prompts nestlings to swallow food items similar to those for adult birds.