Development and functional significance of dorsal air bags in nestlings of Monteiro’s Hornbill Tockus monteiri

  • Colleen Downs
  • Christian Boix-Hinzen
  • Mark Brown

Abstract

This study describes the morphology and investigates the possible function of the air bags found on the nestlings of Monteiro’s Hornbill Tockus monteiri. These air bags increased in size with age and mass of the nestling until 14 d of age, and then decreased in size. By 20 d of age, the air bags were absent. Histological examination of the air bags showed that they were integumentary structures composed of an outer epidermis and an inner dermis. The air bags were not connected to the respiratory system. The body temperature (Tb) of Monteiro’s Hornbill nestlings increased significantly with increasing age. Comparisons of ambient, nest and female body temperatures were made. Female Tb was higher than ambient and nest temperatures. It appears that airbags may provide an effective intermediate insulatory mechanism for the nestlings while they are developing their thermoregulatory ability. Therefore, it is suggested that the dorsal air bags evolved primarily for thermoregulatory benefits to nestlings, although further research is required.

Ostrich 2009, 80(1): 53–58

Author Biographies

Colleen Downs
School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, South Africa
Christian Boix-Hinzen
Percy FitzPatrick Institute, DST/NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa
Mark Brown
School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, South Africa
Section
Articles

Journal Identifiers


eISSN: 1727-947X
print ISSN: 0030-6525