Abstract:Samples of up to ten study skins for each of five species of Microhierax, two species of Polihierax, one species of Spiziapteryx and 23 species of small Falco were measured for 24 dimensions of the head, wings, tail and feet. The logarithmic (log10) valucs of the means of each mcasurcmcnt for each species, and for each sex where dimorphic, were compared using cluster and factor analyses. Microhierux falconets are most similar to the African Pygmy Falcon Polihierax sernitorquatus but are morphometrically distin… Show more
“…9 ). It is common for extant small owls [ 100 ], falconets [ 101 ], and shrikes [ 102 ] to capture insect prey with the hindlimb and use the pes for manipulation during disassembly of insect prey. Fig.…”
Background
Birds are key indicator species in extant ecosystems, and thus we would expect extinct birds to provide insights into the nature of ancient ecosystems. However, many aspects of extinct bird ecology, particularly their diet, remain obscure. One group of particular interest is the bizarre toothed and long-snouted longipterygid birds. Longipterygidae is the most well-understood family of enantiornithine birds, the dominant birds of the Cretaceous period. However, as with most Mesozoic birds, their diet remains entirely speculative.
Results
To improve our understanding of longipterygids, we investigated four proxies in extant birds to determine diagnostic traits for birds with a given diet: body mass, claw morphometrics, jaw mechanical advantage, and jaw strength via finite element analysis. Body mass of birds tended to correspond to the size of their main food source, with both carnivores and herbivores splitting into two subsets by mass: invertivores or vertivores for carnivores, and granivores + nectarivores or folivores + frugivores for herbivores. Using claw morphometrics, we successfully distinguished ground birds, non-raptorial perching birds, and raptorial birds from one another. We were unable to replicate past results isolating subtypes of raptorial behaviour. Mechanical advantage was able to distinguish herbivorous diets with particularly high values of functional indices, and so is useful for identifying these specific diets in fossil taxa, but overall did a poor job of reflecting diet. Finite element analysis effectively separated birds with hard and/or tough diets from those eating foods which are neither, though could not distinguish hard and tough diets from one another. We reconstructed each of these proxies in longipterygids as well, and after synthesising the four lines of evidence, we find all members of the family but Shengjingornis (whose diet remains inconclusive) most likely to be invertivores or generalist feeders, with raptorial behaviour likely in Longipteryx and Rapaxavis.
Conclusions
This study provides a 20% increase in quantitatively supported fossil bird diets, triples the number of diets reconstructed in enantiornithine species, and serves as an important first step in quantitatively investigating the origins of the trophic diversity of living birds. These findings are consistent with past hypotheses that Mesozoic birds occupied low trophic levels.
“…9 ). It is common for extant small owls [ 100 ], falconets [ 101 ], and shrikes [ 102 ] to capture insect prey with the hindlimb and use the pes for manipulation during disassembly of insect prey. Fig.…”
Background
Birds are key indicator species in extant ecosystems, and thus we would expect extinct birds to provide insights into the nature of ancient ecosystems. However, many aspects of extinct bird ecology, particularly their diet, remain obscure. One group of particular interest is the bizarre toothed and long-snouted longipterygid birds. Longipterygidae is the most well-understood family of enantiornithine birds, the dominant birds of the Cretaceous period. However, as with most Mesozoic birds, their diet remains entirely speculative.
Results
To improve our understanding of longipterygids, we investigated four proxies in extant birds to determine diagnostic traits for birds with a given diet: body mass, claw morphometrics, jaw mechanical advantage, and jaw strength via finite element analysis. Body mass of birds tended to correspond to the size of their main food source, with both carnivores and herbivores splitting into two subsets by mass: invertivores or vertivores for carnivores, and granivores + nectarivores or folivores + frugivores for herbivores. Using claw morphometrics, we successfully distinguished ground birds, non-raptorial perching birds, and raptorial birds from one another. We were unable to replicate past results isolating subtypes of raptorial behaviour. Mechanical advantage was able to distinguish herbivorous diets with particularly high values of functional indices, and so is useful for identifying these specific diets in fossil taxa, but overall did a poor job of reflecting diet. Finite element analysis effectively separated birds with hard and/or tough diets from those eating foods which are neither, though could not distinguish hard and tough diets from one another. We reconstructed each of these proxies in longipterygids as well, and after synthesising the four lines of evidence, we find all members of the family but Shengjingornis (whose diet remains inconclusive) most likely to be invertivores or generalist feeders, with raptorial behaviour likely in Longipteryx and Rapaxavis.
Conclusions
This study provides a 20% increase in quantitatively supported fossil bird diets, triples the number of diets reconstructed in enantiornithine species, and serves as an important first step in quantitatively investigating the origins of the trophic diversity of living birds. These findings are consistent with past hypotheses that Mesozoic birds occupied low trophic levels.
“…Tail-pumping has been observed in several small species of raptors (e.g. Maclean, 1970;Tarboton, 1978;Kemp and Crowe, 1994;Kemp and Van Zyl, 1998;Kemp and Vidhidharm, 1998). Tail-pumping by Black-thighed Falconets (Microhierax fringillarius) may act as an excited post-flight display (Kemp and Crowe, 1994).…”
Section: Introductionmentioning
confidence: 99%
“…Maclean, 1970;Tarboton, 1978;Kemp and Crowe, 1994;Kemp and Van Zyl, 1998;Kemp and Vidhidharm, 1998). Tail-pumping by Black-thighed Falconets (Microhierax fringillarius) may act as an excited post-flight display (Kemp and Crowe, 1994). Kemp and Vidhidharm (1998) found that male White-rumped Pygmy Falcons (Polihierax insignis) tail-pumped in response to playback of the calls of conspecific males, suggesting that tail-pumping may function as an aggressive territorial warning to potential intruders.…”
When perched, several species of small falcons, including American Kestrels (Falco sparverius), often pump their tails, but the possible function of this behaviour is unknown. Our objective was to use observations and experiments to examine the possible function(s) of tail-pumping by American Kestrels. Fieldwork was conducted from March 2015 to December 2015 at the Blue Grass Army Depot in Madison County, Kentucky. During observations of focal kestrels, we noted their behaviour (e.g. landing on a perch, hunting, or consuming prey), including when and how often they pumped their tails (i.e. rapid movement of the tail down, then back up to its original position). Kestrels typically tail-pumped when landing on a perch (mean = 4.1±0.2 pumps per 10 s) and consuming prey (mean = 2.4±0.2 pumps per 10 s). When hunting, kestrels tail-pumped at higher rates during the 30 s prior to attacking (mean = 1.1±0.3 pumps) than they did during the 30–60 s interval before an attack (mean = 0.3±0.1 pumps). During experiments where kestrels were presented with models of a conspecific and a predator (Cooper's Hawk, Accipiter cooperi), we found no difference in rates of tail-pumping prior to and during the presentation. These results suggest that tail-pumping by American Kestrels is not used either to communicate with conspecifics or as a predator-deterrent signal. Rather, kestrels appear to tail-pump to help maintain balance on perches when landing and consuming prey. In addition, prior to attacking prey, kestrels typically bob their heads (possibly to aid in judging distances), and tail-pumping may help them maintain stability as they head-bob and prepare to attack.
“…We enjoyed good relationships with Roy Siegfried and the Percy FitzPatrick Institute of African Ornithology at Cape Town, and worked especially closely with Tim Crowe as he held our hand through analysis and interpretation of our data on raptor morphometrics and hornbill systematics, and on the role museums should play in these endeavours (Kemp and Crowe 1985, Crowe et al 1989, Kemp and Crowe 1990, 1994. Conservation biology was coming of age when Siegfried asked us to supervise two of his students in a year-long study of rare birds in northern Kruger but we extended this project to three years, with motivational support of Quentin Pretorius and his financial backing from Southern Life.…”
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