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Moas, kiwis, Hesperornis, and kicking secretary birds
Some recent (and not so recent) bird items that may be of interest:
Marie R. G. Attard, Laura A. B. Wilson, Trevor H. Worthy, Paul
Scofield, Peter Johnston, William C. H. Parr & Stephen Wroe (2016)
Moa diet fits the bill: virtual reconstruction incorporating mummified
remains and prediction of biomechanical performance in avian giants.
Proceedings of the Royal Society B 283 20152043
The moa (Dinornithiformes) are large to gigantic extinct terrestrial
birds of New Zealand. Knowledge about niche partitioning, feeding mode
and preference among moa species is limited, hampering
palaeoecological reconstruction and evaluation of the impacts of their
extinction on remnant native biota, or the viability of exotic species
as proposed ecological ‘surrogates'. Here we apply three-dimensional
finite-element analysis to compare the biomechanical performance of
skulls from five of the six moa genera, and two extant ratites, to
predict the range of moa feeding behaviours relative to each other and
to living relatives. Mechanical performance during biting was compared
using simulations of the birds clipping twigs based on muscle
reconstruction of mummified moa remains. Other simulated food
acquisition strategies included lateral shaking, pullback and
dorsoventral movement of the skull. We found evidence for limited
overlap in biomechanical performance between the extant emu (Dromaius
novaehollandiae) and extinct upland moa (Megalapteryx didinus) based
on similarities in mandibular stress distribution in two loading
cases, but overall our findings suggest that moa species exploited
their habitats in different ways, relative to both each other and
extant ratites. The broad range of feeding strategies used by moa, as
inferred from interspecific differences in biomechanical performance
of the skull, provides insight into mechanisms that facilitated high
diversities of these avian herbivores in prehistoric New Zealand.
Andrei V. Zinoviev (2015)
Comparative anatomy of the intertarsal joint in extant and fossil
birds: inferences for the locomotion of Hesperornis regalis
(Hesperornithiformes) and Emeus crassus (Dinornithiformes).
Journal of Ornithology 156: Supplement 1: 317-323
Reconstruction of the soft tissues (i.e., collateral ligaments, Lig.
anticum, menisci, tendon of the M. fibularis brevis) involved in the
mechanism of intertarsal joint stabilization in two species of extinct
birds, Hesperornis regalis and Emeus crassus, allowed insights into
their locomotion. The foot-propelled diving of Hesperornis included
loon-like movement of the tarsometatarsus and grebe-like movement of
the toes. Movement of the tarsometatarsus in Emeus was restricted to
the parasagittal plane, thus resembling those of other Ratites and
most highly cursorial birds.
Diana Le Duc , Gabriel Renaud, Arunkumar Krishnan, Markus Sällman
Almén, Leon Huynen, Sonja J. Prohaska, Matthias Ongyerth, Bárbara D.
Bitarello, Helgi B. Schiöth, Michael Hofreiter, Peter F. Stadler, Kay
Prüfer, David Lambert, Janet Kelso & Torsten Schöneberg (2015)
Kiwi genome provides insights into evolution of a nocturnal lifestyle.
Genome Biology 16: 147
Kiwi, comprising five species from the genus Apteryx, are endangered,
ground-dwelling bird species endemic to New Zealand. They are the
smallest and only nocturnal representatives of the ratites. The timing
of kiwi adaptation to a nocturnal niche and the genomic innovations,
which shaped sensory systems and morphology to allow this adaptation,
are not yet fully understood.
We sequenced and assembled the brown kiwi genome to 150-fold coverage
and annotated the genome using kiwi transcript data and non-redundant
protein information from multiple bird species. We identified
evolutionary sequence changes that underlie adaptation to nocturnality
and estimated the onset time of these adaptations. Several opsin genes
involved in color vision are inactivated in the kiwi. We date this
inactivation to the Oligocene epoch, likely after the arrival of the
ancestor of modern kiwi in New Zealand. Genome comparisons between
kiwi and representatives of ratites,Galloanserae, and Neoaves,
including nocturnal and song birds, show diversification of kiwi’s
odorant receptors repertoire, which may reflect an increased reliance
on olfaction rather than sight during foraging. Further, there is an
enrichment of genes influencing mitochondrial function and energy
expenditure among genes that are rapidly evolving specifically on the
kiwi branch, which may also be linked to its nocturnal lifestyle.
The genomic changes in kiwi vision and olfaction are consistent with
changes that are hypothesized to occur during adaptation to nocturnal
lifestyle in mammals. The kiwi genome provides a valuable genomic
resource for future genome-wide comparative analyses to other extinct
and extant diurnal ratites.
Steven J. Portugal, Campbell P. Murn, Emily L. Sparkes & Monica A. Daley (2016)
The fast and forceful kicking strike of the secretary bird.
Current Biology26(2): pR58–R59
DOI: http://dx.doi.org/10.1016/j.cub.2015.12.004 |
The study of animal locomotion has uncovered principles that can be
applied to bio-inspired robotics, prosthetics and rehabilitation
medicine, while also providing insight into musculoskeletal form and
function . In particular, study of extreme behaviors can reveal
mechanical constraints and trade-offs that have influenced evolution
of limb form and function . Secretary birds (Sagittarius serpentarius;
Figure 1 A) are large terrestrial birds of prey endemic to sub-Saharan
Africa, which feed on snakes, lizards and small mammals. They
frequently kick and stamp on the prey’s head until it is killed or
incapacitated, particularly when dispatching larger lizards and
venomous snakes . The consequences of a missed strike when hunting
venomous snakes can be deadly, so the kicking strikes of secretary
birds require fast yet accurate neural control. Delivery of fast,
forceful and accurate foot strikes that are sufficient to stun and
kill prey requires precision targeting, demanding a high level of
coordination between the visual and neuromuscular systems.