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Cranium and premaxilla of kākāpō (Strigops habroptilus; LB14836). A, Left lateral view with rhinotheca in place; B, ventral view with rhinotheca removed to show exposed premaxilla. Photograph: J Froggatt.
Source publication
We describe the upper portion of the bill sheath (rhinotheca) of the kākāpō (Strigops habroptilus) from three adult female specimens. The external buccal surface of the rhinotheca is deeply concave with a prominent palatal stop and hardened chevrons creating a ‘milling apparatus’ that the kākāpō uses to grind food. The palatal stop presents a worki...
Contexts in source publication
Context 1
... internal surface lies in contact with the premaxillary bone and is not visible on a live or intact dead bird. Figure 1 shows a kākāpō cranium and premaxilla with the rhinotheca in place ( Figure 1A) and placed beside the premaxilla ( Figure 1B). Figure 2 shows the isolated lower part of the kākāpō rhinotheca showing the external surface ( Figure 2A) and normally-hidden internal surface that contacts the pre- maxillary bone (Figure 2B-D). ...
Context 2
... internal surface lies in contact with the premaxillary bone and is not visible on a live or intact dead bird. Figure 1 shows a kākāpō cranium and premaxilla with the rhinotheca in place ( Figure 1A) and placed beside the premaxilla ( Figure 1B). Figure 2 shows the isolated lower part of the kākāpō rhinotheca showing the external surface ( Figure 2A) and normally-hidden internal surface that contacts the pre- maxillary bone (Figure 2B-D). ...
Context 3
... internal surface lies in contact with the premaxillary bone and is not visible on a live or intact dead bird. Figure 1 shows a kākāpō cranium and premaxilla with the rhinotheca in place ( Figure 1A) and placed beside the premaxilla ( Figure 1B). Figure 2 shows the isolated lower part of the kākāpō rhinotheca showing the external surface ( Figure 2A) and normally-hidden internal surface that contacts the pre- maxillary bone (Figure 2B-D). ...
Context 4
... rhinotheca of the kākāpō is broad and deeply concave ( Figures 1B, 4A) with the prox- imal third forming a smooth, slightly concave, ledge (Figure 2A, 'L'). The surface then rises abruptly towards the premaxilla at an angle of about 55° from the horizontal (when placed on a flat surface), forming an overhang (see cross-section, Figure 2E). ...
Context 5
... thickness is not uniform throughout the cross-section, the maximum thickness being 5.6 mm at the region of the stop/abutment, and the minimum being 2.1 mm further towards the tip of the bill. The surface of the overlying premaxilla ( Figure 1B, upper) has an abutment and pattern of chevron marks that approximately mirror those on the internal surface of the rhinotheca ( Figure 2B). However, the premaxilla's surface features are smoothed out and less pronounced. ...
Citations
... Access to resources shapes species' physiology and behaviour across taxa, e.g. foraging-related differences in bill shape in parrots (Homberger 2003;Froggatt and Gill 2016), or the distinctive probe-like morphology of the middle finger of the aye-aye (Daubentonia madagascariensis) (Sterling and McCreless 2006). Occasionally, resources are concealed or difficult to access in ways which present a particular cognitive challenge that is addressed through behavioural adaptations. ...
Access to resources shapes species’ physiology and behaviour. Water is not typically considered a limiting resource for rainforest-living chimpanzees; however, several savannah and savannah-woodland communities show behavioural adaptations to limited water. Here, we provide a first report of habitual well-digging in a rainforest-living group of East African chimpanzees ( Pan troglodytes schweinfurthii ) and suggest that it may have been imported into the community’s behavioural repertoire by an immigrant female. We describe the presence and frequency of well-digging and related behaviour, and suggest that its subsequent spread in the group may have involved some degree of social learning. We highlight that subsurface water is a concealed resource, and that the limited spread of well-digging in the group may highlight the cognitive, rather than physical, challenges it presents in a rainforest environment.
... Their presence adds to the sensory repertoire used by moa to negotiate their environment; for example, a combination of olfaction and bill sensation would allow foraging among foliage in a context of low light or reduced visual acuity. The bill tip organ is also present in Kakapo [78], as in some other parrots. There are appear to be no comparative data on trigeminal ganglion endocast size, but the prominent structure in M. didinus is consistent with bill sensation as a major component of the sensory toolkit [79]. ...
Avian cranial anatomy is constrained by the competing (or complementary) requirements and costs of various facial, muscular, sensory, and central neural structures. However, these constraints may operate differently in flighted versus flightless birds. We investigated cranial sense organ morphology in four lineages of flightless birds: kiwi (Apteryx), the Kakapo (Strigops habroptilus), and the extinct moa (Dinornithiformes) from New Zealand; and the extinct elephant birds from Madagascar (Aepyornithidae). Scleral ring and eye measurements suggest that the Upland Moa (Megalapteryx didinus) was diurnal, while measurements for the Kakapo are consistent with nocturnality. Kiwi are olfactory specialists, though here we postulate that retronasal olfaction is the dominant olfactory route in this lineage. We suggest that the Upland Moa and aepyornithids were also olfactory specialists; the former additionally displaying prominent bill tip sensory organs implicated in mechanoreception. Finally, the relative size of the endosseous cochlear duct revealed that the Upland Moa had a well-developed hearing sensitivity range, while the sensitivity of the kiwi, Kakapo, and aepyornithids was diminished. Together, our results reveal contrasting sensory strategies among extant and extinct flightless birds. More detailed characterisation of sensory capacities and cranial anatomy in extant birds may refine our ability to make accurate inferences about the sensory capacities of fossil taxa.
Allen’s rule is an ecogeographical pattern whereby the size of appendages of animals increases relative to body size in warmer climates in order to facilitate heat exchange and thermoregulation. Allen’s rule predicts that one consequence of a warming climate would be an increase in the relative size of appendages, and evidence from other bird species suggests that this might be occurring. Using measurements from museum specimens, we determined whether spatio-temporal variation in bills and legs of Australian Pachycephalidae species exhibits within-species trends consistent with Allen’s rule and increases in temperature attributable to climatic warming. We conducted regression model analyses relating appendage size to spatio-temporal variables, while controlling for body size. The relative bill size in four of the eight species was negatively associated with latitude. Tarsus length showed no significant trends consistent with Allen’s rule. No significant increases in appendage size were found over time. Although bill size in some species was positively correlated with warmer temperatures, the evidence was not substantial enough to suggest a morphological response to climatic warming. This study suggests that climate change is not currently driving adaptive change towards larger appendages in these species. We suggest that other adaptive mechanisms might be taking place.
