Interspecific competition between introduced house finch populations and two associated passerine species

Summary House Finches (Carpodacus mexicanus), natives of western North America, have expanded their range in the eastern United States since their 1940 release in New York City. Range and the relation of House Finch population growth to the population dynamics of House Sparrows (Passer domesticus) and Purple Finches (Carpodacus purpureus) were examined, using data from the Breeding Bird Survey and the Christmas Bird Count. The House Finch population grew exponentially throughout its eastern range. Significant negative relationships in population density, relative to spatial and temporal control populations, were found between House Finches and House Sparrows in summer and winter, and between House Finches and Purple Finches in summer. Purple Finch and House Sparrow populations outside of the House Finch range appeared to have no effect on each other throughout the study. Neither changes in 74 weather variables, nor changes in forest, field or developed habitat explained the observed trends in population density. The results indicate that House Finches compete with these two species, but winter migration complicates the picture.     

The visual fields of two ground‐foraging birds,House Finches and House Sparrows,allow for simultaneous foraging and anti‐predator vigilance

In birds, differences in the extent and position of the binocular visual field reflect adaptations to varying foraging strategies, and the extent of the lateral portion of the field may reflect anti‐predator strategies. The goal of this study was to describe and compare the visual fields of two ground‐foraging passerines, House Finch Carpodacus mexicanus and House Sparrow Passer domesticus. We found that both species have a binocular field type that is associated with the accurate control of bill position when pecking. Both species have eye movements of relatively large amplitude, which can produce substantial variations in the configuration of the binocular fields. We propose that in these ground foragers, their relatively wide binocular fields could function to increase foraging efficiency by locating multiple rather than single food items prior to pecking events. The lateral fields of both species are wide enough to facilitate the detection of predators or conspecifics while head‐down foraging. This suggests that foraging and scanning are not mutually exclusive activities in these species, as previously assumed. Furthermore, we found some slight, but significant, differences between species: House Sparrow binocular fields are both wider and vertically taller, and the blind area is wider than in House Finches. These differences may be related to variations in the degree of eye movements and position of the orbits in the skull.     

Conspecific-only experience during development reduces the strength of heterospecific song discrimination in Zebra Finches (Taeniopygia guttata): a test of the optimal acceptance threshold hypothesis

Conspecifics during development provide the most reliable sensory cues for species recognition in parental bird species. The Zebra Finch (Taeniopygia guttata) is a sexually dimorphic model species used for investigations of the behavioural cues and neurobiological substrates of species recognition. Regarding acoustic conspecific cues, theory predicts that exposure to both con- and heterospecific vocalisations and other environmental sounds results in more accurate auditory species discrimination, because diverse vocal cues during development shift optimal conspecific acceptance thresholds to be more restrictive to yield fewer acceptance errors. We tested the behavioural preferences of female and male Zebra Finches raised in an outdoor environment (Control) and female and male Zebra Finches reared in an indoor colony with exposure to Zebra Finches only (Restricted), to playbacks of songs of Zebra Finches, Zebra Finches cross-fostered by Bengalese Finches (Lonchura striata var. domestica), and Bengalese Finches. Several behavioural measures revealed minimal sexual dimorphism in discrimination but showed that Control subjects preferred conspecifics’ songs over either the songs of cross-fostered Zebra Finches or Bengalese Finches. Restricted Zebra Finches in contrast did not discriminate behaviourally between the three song types. These results support the concept of a shift in the species acceptance threshold in the restricted treatment resulting in more acceptance errors. We discuss future work to test the role of exposure to diverse vocal cues of both con- and heterospecifics in the ontogeny of song perception in this important laboratory model species for social recognition research.     

Song Learning in Wild and Domesticated Strains of White‐Rumped Munia,Lonchura striata,Compared by Cross‐Fostering Procedures: Domestication Increases Song Variability by Decreasing Strain‐Specific Bias

Song diversity results from the interactions between natural selection, sexual selection, and individual learning. To understand song diversity, all three factors must be considered collectively, not separately. Bengalese Finches were domesticated about 250 yr ago. Their courtship songs have become different from their ancestor, the White‐rumped Munia. Bengalese Finches sing songs with complex note‐to‐note transition patterns and with acoustically diverse song notes while White‐rumped Munias sing songs with fixed note sequence and mostly broad band song notes. Bengalese Finches were selected for domestication based on their good parenting ability, not their songs, but this artificial selection has nonetheless affected their songs. To test whether divergence occurred not only in the song phenotypes but also in the genetic basis for predisposition of strain specific song learning, we conducted a cross‐fostering experiment between Bengalese Finches and White‐rumped Munias. In both strains, song learning was affected by rearing condition: the acoustical feature and transition patterns followed those of the foster fathers. However, the accuracy of song learning differed between the wild and the domesticated strains: sharing of song note between sons and tutors in Finches was not very accurate regardless of the tutor, while Munias were highly accurate in copying Munia songs but often omitted song elements from Finch fathers. These results suggest that White‐rumped Munias are strongly constrained to learn their own strain’s song, and that this constraint was relaxed in the Bengalese Finch by domestication.     

Breeding ecology and nest site selection in allopatric mainland Citril Finches Carduelis[citrinella] citrinella and insular Corsican Finches Carduelis[citrinella] corsicanus

The breeding ecology and nest site selection of mainland Citril Finches and insular Corsican Finches have been studied throughout their limited range. For many years both endemic forms were considered to be two sub-species; however, based on evidence from more recent molecular studies they have been split into two species. This study provides data on the variations in breeding ecology and nest site selection in the different sub-populations of these little studied species. A secondary aim was to search out evidence of ecological differentiation between mainland Citril Finches and insular Corsican Finches. We found that the studied sub-populations of both species largely overlapped in breeding ecology. Our data confirms the close similarity of Citril Finches and Corsican Finches, both which are, similar to mountain birds, well adapted to the local habitat conditions of their different mountain systems. Several differences were identified within the studied sub-populations of the two (sub-) species with respect to nest site selection, probably caused by environmental conditions and local predators. One of the main differences between the two species is that Citril Finches breed mainly in half-open conifer forests (especially pine forests), while Corsican Finches breed in the more open scrubby mountains of the Mediterranean islands dominated mainly by the Tree Heath as an adaptation to the different landscapes on the islands. In contrast to Citril Finches, this preference of the Corsican Finches for Tree Heath as nesting plants – even if suitable pines are available – is typical of the species. These behavioural changes result in a niche expansion into open habitats at lower altitudes. We suggest that the observed niche expansion and behavioural variations are not suitable criteria for taxonomic status, a proposal in contrast to that of Sangster [Ibis 142:487–490 (2000)]. We further suggest that the few ecological differences found in this study between the two (sub-)species are the result of the so-called insular syndrome, which includes changes in life history traits such as morphology, demography and behaviour.     

Device to Prepare Extruded Nuclei and Chromosome Squashes

A horizontal toggle clamp mounted on a rigid base plate makes nuclear extrusion and polytene chromosome squashing simple and reproducible. The base plate has a stage with shallow flat grooves to align the tissue sample directly below the clamp's swivel foot and hold the microscope slide in place during squashing. Appropriate pressure to obtain either extruded nuclei or squash preparations of polytene chromosomes is established empirically by adjusting the clamp's spindle assembly up or down.     

Evaluating foot kinematics using magnetic resonance imaging: from maximum plantar flexion, inversion, and internal rotation to maximum dorsiflexion, eversion, and external rotation

The foot consists of many small bones with complicated joints that guide and limit motion. A variety of invasive and noninvasive means [mechanical, X-ray stereophotogrammetry, electromagnetic sensors, retro-reflective motion analysis, computer tomography (CT), and magnetic resonance imaging (MRI)] have been used to quantify foot bone motion. In the current study we used a foot plate with an electromagnetic sensor to determine an individual subject's foot end range of motion (ROM) from maximum plantar flexion, internal rotation, and inversion to maximum plantar flexion, inversion, and internal rotation to maximum dorsiflexion, eversion, and external rotation. We then used a custom built MRI-compatible device to hold each subject's foot during scanning in eight unique positions determined from the end ROM data. The scan data were processed using software that allowed the bones to be segmented with the foot in the neutral position and the bones in the other seven positions to be registered to their base positions with minimal user intervention. Bone to bone motion was quantified using finite helical axes (FHA). FHA for the talocrural, talocalcaneal, and talonavicular joints compared well to published studies, which used a variety of technologies and input motions. This study describes a method for quantifying foot bone motion from maximum plantar flexion, inversion, and internal rotation to maximum dorsiflexion, eversion, and external rotation with relatively little user processing time.     

辽宁大学生足的尺寸和形态的研究

目的探明辽宁地区大学生的足形发育现状。方法采用国际通用的足部测量学方法,调查了辽宁籍汉族大学生319（男156,女163）名。结果辽宁男女大学生足部测量值均比日本相应值小。各测量值有明显的性差,也存在左右差,其中足长右侧>左侧分别男性为23.1%、女性34.4%;右侧=左侧男性为21.8%、女性为47.2%;右侧<左侧男性为 55.1 %、女性为 18.4%, 男女性左右差的构成比有显著性差异。 足型构成比以中间型最多, 男性占 80.1 %, 女性占 81.0%;短宽型男性占 12.2%, 女性占 8.6%;窄长型男性 占7.7 %, 女性占 10.4 %。 结论 辽宁男女大学生足形相对较短窄瘦, 足长和足宽有明显的民族差和 地区差。     

Notes on Technic

A horizontal toggle clamp mounted on a rigid base plate makes nuclear extrusion and polytene chromosome squashing simple and reproducible. The base plate has a stage with shallow flat grooves to align the tissue sample directly below the clamp's swivel foot and hold the microscope slide in place during squashing. Appropriate pressure to obtain either extruded nuclei or squash preparations of polytene chromosomes is established empirically by adjusting the clamp's spindle assembly up or down.     

Triploid ZZZ Zebra Finches Taeniopygia guttata exhibit abnormal sperm heads and poor reproductive performance

Here we report the first discovery of two viable triploid male Zebra Finches Taeniopygia guttata. We compared the morphology of their sperm with that of normal diploid Zebra Finches and examined eggs resulting from a triploid male and diploid female pairing to investigate whether triploid Zebra Finches can reproduce. The majority (78%) of the triploids' spermatozoa had malformed sperm heads, which were 60% larger, and all examined eggs (n = 42) were infertile. Our results tentatively suggest that triploid ZZZ Zebra Finches cannot reproduce, and thus represent a rare evolutionary dead‐end.     

Crocodylian and mammalian carnivore feeding traces on hominid fossils from FLK 22 and FLK NN 3, Plio-Pleistocene, Olduvai Gorge, Tanzania

Taphonomic analysis of the Olduvai Hominid (OH) 8 left foot from FLK NN Level 3 and the OH 35 left leg from FLK Level 22 (Zinjanthropus level) in Middle Bed I, Olduvai Gorge, indicates that both were fed upon by crocodiles. Both bear extensive tooth marking, including bisected tooth marks diagnostic of crocodylian feeding. The location of the bisected tooth marks on the distal tibia and the talus indicates disarticulation of the foot by crocodiles. The broken proximal ends of the tibia and fibula are more typical of feeding by a leopard-like carnivore, as is damage to the OH 7 mandible and parietals that are associated with and may derive from the same individual as OH 8. Previous work showing a close articulation of the foot and the leg has been used to suggest that the two specimens belong to the same individual despite deriving from sites separated by 200 m and slightly different stratigraphic levels according to previous work. The location and agent of tooth marking and the nature of gross damage do not refute this hypothesis, but the punctures on the talus and distal tibia differ in size and sharpness. Recent work shows that the stratigraphic discrepancy between OH 8 and OH 35 is greater than previously thought, refuting the single-individual hypothesis. Although seemingly unlikely, this denotes that two hominids represented by rarely found leg and foot elements both lost their left foot to crocodiles at nearby sites within a 6,000 year interval. We cannot determine if the hominids were preyed upon by crocodiles or mammalian carnivores. However, the carnivore damage to them and associated faunal remains suggests that high predation risk constrained hominid activities involving discard of the stone artifacts found at these sites. This finding is inconsistent with the interpretation of the sites as home bases or living floors.     

Competition for resources mediated by intrinsic social dominance in sympatric finches

Gouldian Erythrura gouldiae and Long‐tailed Finches Poephila acuticauda are morphologically and ecologically similar sympatric species, for which social dominance relationships are likely to determine access to critical limiting resources. Building on previous research showing that Long‐tailed Finches dominate competition for nest‐sites, I staged dyadic contests for food between the two species in captivity in order to test social dominance dynamics under controlled conditions. Long‐tailed Finches were likely to dominate interactions with Gouldian Finches and expressed higher levels of aggression while competing for access to food. These results suggest a stable dominance relationship between the two species which could be affecting Gouldian Finches' access to food resources in the wild, potentially constraining their ability to recover from recent population declines.     

Leukocyte Profiles in Wild House Finches with and without Mycoplasmal Conjunctivitis,a Recently Emerged Bacterial Disease

Leukocyte profiles (relative numbers of white blood cell types) have been used by a growing number of ecological studies to assess immune function and stress in wild birds. House Finches (Carpodacus mexicanus) in eastern North America are susceptible to an eye disease caused by the bacterium Mycoplasma gallisepticum, providing the opportunity to examine whether leukocyte profiles are associated with infection status and other host characteristics. In this study, we compared blood smears from 297 wild House Finches with and without conjunctivitis to examine whether leukocyte profiles were associated with the presence and severity of mycoplasmal conjunctivitis. We also evaluated the influence of age, sex, and molt on leukocyte profiles in both diseased and nondiseased birds. Of 243 House Finches of known age and sex sampled, 30% showed clinical signs of mycoplasmal conjunctivitis. House Finches with conjunctivitis had significantly higher heterophil to lymphocyte (H/L) ratios and harbored greater numbers and proportions of heterophils and monocytes than nondiseased birds. Leukocyte profiles of noninfected birds did not differ significantly with respect to sex, but young birds had significantly greater numbers of lymphocytes and total white blood cells than adults. Molting birds had significantly more eosinophils than nonmolting birds. Finally, House Finches with the most severe outward signs of conjunctivitis showed the most dramatic leukocyte changes relative to noninfected individuals, and increasing H/L ratios and monocytes in diseased birds were paralleled in a subset of birds that were recaptured during the study period. These results are consistent with patterns observed in domestic poultry and suggest that understanding patterns of leukocyte differentials in this host-pathogen system could improve our understanding of innate immunity and infectious disease risk in other wild passerines.     

Age-related,interindividual, and right/left differences in anterior-posterior foot pressure ratio in preschool children

Background

This study aimed to examine age-related, interindividual, and right/left differences in anterior-posterior foot pressure ratio in 764 preschool children (364 boys and 400 girls) aged 3.5-6.5 years.

Methods

Subjects maintained an upright standing posture for 10 seconds on the Footview Clinic, an instrument designed to calculate the anterior-posterior foot pressure ratio. The ratio of anterior foot pressure in each subject’s right and left feet was selected as a variable, and the mean of a 10 s measurement was used for analysis.

Results

The ratio of anterior foot pressure was significantly larger in the right foot than in the left foot. With regard to age, the ratio of anterior foot pressure was significantly larger in children aged over 4.5 years than in children aged 3.5 years. It was also larger in children aged 6 and 6.5 years than in children aged 4 years. Interindividual differences in variables were large, and coefficients of variance were highest in children aged 3.5 years and lowest in children aged 6.5 years.

Conclusions

In conclusion, anterior foot pressure increases with age in preschool children. Interindividual differences in anterior foot pressure are large and tend to decrease with age. Furthermore, the anterior foot pressure is slightly higher in the right foot than in the left foot. These results will be useful for various studies, such as examining relationships between the anterior-posterior foot pressure ratio and factors, such as untouched toes, physical fitness, and level of exercise.     

Conservation status of landbirds on Floreana: the smallest inhabited Galápagos Island

On Floreana, the smallest inhabited island in the Galápagos, populations of several species of birds have either been extirpated or, based on anecdotal evidence and small‐scale surveys, are declining. Our objective, therefore, was to conduct a comprehensive survey of landbirds encompassing the entire island during three breeding seasons (2014–2016). We conducted surveys at 59 points in 2014, 257 in 2015, and 295 in 2016. Each survey point was sampled once. We detected 12 species during our surveys. Galápagos Flycatchers, Yellow Warblers, Small and Medium ground‐finches, and Small Tree‐Finches were widely distributed over the entire island. Common Cactus‐Finches and Medium Tree‐Finches had more restricted distributions in the lower or higher parts of the island. Few Dark‐billed Cuckoos (Coccyzus melacoryphus), Paint‐billed Crakes (Neocrex erythrops), Galápagos Doves (Zenaida galapagoensis), and Galápagos Short‐eared Owls (Asio flammeus galapagoensis) were recorded. Small Ground‐Finches and Small Tree‐Finches were found at densities comparable to those on other Galápagos Islands, whereas densities of Galápagos Flycatchers and Yellow Warblers were higher on Floreana than on other islands. Endemic Medium Tree‐Finches were confined to an area of 24 km², mainly in the highlands, but were still widespread and common in their restricted habitat, with the number of territories estimated to be between 3900 and 4700. Of 22 originally occurring landbirds on Floreana, no fewer than 10 species have either been extirpated or are likely to have been extirpated since the arrival of the first human inhabitants. The combined effects of introduced mammals, large‐scale habitat destruction, and direct human persecution were responsible for the extirpation of six species during the 19th century. Three additional species have been extirpated since 1960, likely due to the introduction of the parasitic fly Philornis downsi, and this fly remains a major threat for the remaining bird species. Developing strategies for reducing the impact of these flies on the birds of the Galapagos Islands must be a high priority. In addition, habitat management and restoration, including the control of invasive plants and promotion of native tree species, will be critically important in conserving landbird populations on Floreana.     

The effects of elevated testosterone on plumage hue in male House Finches

The majority of studies examining the role of hormones in the proximate mechanisms of plumage coloration in birds have focused on intersexual differences (plumage dichromatism) and on structural- or melanin-based plumage coloration. The relationship between hormones and carotenoid-based plumage color, and in particular intrasexual plumage color variation, has received little attention. We manipulated testosterone levels of both captive and wild male House Finches to determine whether testosterone influences the expression of male plumage color in this species. We found that in captive male House Finches elevated testosterone delayed molt and resulted in drabber, less red plumage, even when birds were supplemented with dietary carotenoids. Elevated testosterone also resulted in drab plumage color in wild males, and appeared to delay molt in wild birds as well. Wild males implanted with testosterone showed wide variation in expression of plumage coloration. Those implanted early in the year molted plumage similar in color to their pre-treatment plumage, but those implanted later molted substantially duller plumage, possibly because delayed molt resulting from elevated testosterone caused these males to molt when carotenoid pigments were not available in sufficient amounts. These observations have the potential to explain previously reported relationships between plumage color and behavior in male House Finches, and highlight the importance of considering the proximate mechanisms of plumage coloration in avian sexual selection.     

Lateralisation in birds of prey: adaptive and phylogenetic considerations

Lateralisation, the different use of one or other side or appendix of the body, is basically determined by brain asymmetry which, in turn, is likely to be due to adaptive reasons. Several studies have been carried out on birds in general. However, birds of prey in particular, although they are very good candidates, have not been investigated from the sensory lateralisation point of view. In fact, many species scan for prey while perched and capture terrestrial prey with the feet, having at the same time the obvious necessity to keep their balance. This paper, therefore, investigates the existence of some sort of lateralisation in several species of both Falconiformes and Strigiformes temporarily in captivity. Attention is given to: (a) the direction of body rotation when perceiving a sound stimulus from behind the body and (b) the use of the feet when grasping a terrestrial prey. Lateralisation was found to be clearly present in both types of tests, although with some difference in its expression. In fact, almost every species tested rotated its body anti-clockwise, i.e. to the left, both in the first test and in repeated tests, with no noticeable difference between Falconiformes and Strigiformes. Also prey grasping showed a preferential use of one foot. Falconiformes preferred clearly to grasp the prey with one foot only in both the first test and in subsequent ones. Strigiformes, on the other hand, preferred using both feet, although a not insignificant proportion of individuals used one foot. Only the little owl seemed to have the tendency to prefer to use the right foot only, in a similar manner to Falconiformes. In fact, this bird is the most "diurnal" owl species among those tested, suggesting that lateralisation in footedness might be affected by adaptive constraints more than by phylogenetic similarities. Lateralisation, therefore, seems to be very widespread among birds of prey. Preferential use of the right foot also appears to be a general habit, and this is probably connected to the use of left hemisphere when manipulating food items.     

Toxic,invasive treefrog creates evolutionary trap for native gartersnakes

Possession of unique defensive toxins by nonindigenous species may increase the likelihood of creating evolutionary traps for native predators. We tested the hypothesis that nonindigenous, toxic Cuban Treefrogs (Osteopilus septentrionalis) have created an evolutionary trap for native, generalist snakes. Additionally, we explored the possibility that populations of snakes that co-occur with Cuban Treefrogs have responded in ways that allow them to escape potential trap dynamics. To evaluate a potential fitness cost of consuming Cuban Treefrogs, we monitored growth of 61 wild-caught Common Gartersnakes (Thamnophis sirtalis) fed exclusive diets of either Cuban Treefrogs, native Green Treefrogs (Hyla cinerea), or native Golden Shiners (Notemigonus crysoleucas). Snakes in the Cuban Treefrog diet treatment gained less than half the mass of those consuming native prey, and Cuban Treefrogs were significantly less digestible than native prey. There was no difference in the response of gartersnakes to prey scent cues of Cuban Treefrogs and Green Treefrogs. Our results indicate that Cuban Treefrogs likely represent an evolutionary trap for snakes because consumption of these frogs carries fitness costs, yet snakes fail to recognize this prey as being costly. We found no difference in growth or response to prey cues between snakes from invaded and non-invaded regions, suggesting snakes have not responded to escape trap dynamics. Interactions of native snakes and Cuban Treefrogs support the idea that introduced species with novel toxins may increase the likelihood of evolutionary trap formation.     

Moult,breeding season,mass, wing length,and dispersal in Cape Robins (Cossypha caffra) and Olive Thrushes (Turdus olivaceus): results from mist-netting garden birds

We compared a data set from the Western Cape, South Africa (GDU, n = 170 Olive Thrushes (Turdus olivaceus), n = 475 Cape Robins (Cossypha caffra)) with our captures in the Eastern Cape, South Africa (n = 197 Olive Thrushes, n = 203 Cape Robins). In both regions Olive Thrushes began moult in December-January, while wing-moult lasted for 89 days in the Western Cape compared to 53 days in the Eastern Cape. Cape Robins began moult in early November in the Western Cape, early January in the Eastern Cape and again the duration of wing-moult was longer in the Western Cape (64 days) than in the Eastern Cape (50 days). For both species the start of moult coincided with the end of the breeding season. Cape Robins were heavier and longer-winged in the Western Cape than in the Eastern Cape. There was no significant difference in mean mass or mean wing length of the Olive Thrush between the two provinces. Both ringing and atlas data suggest that Cape Robins are relatively more common than Olive Thrushes in the Western Cape, but not in the Eastern Cape. In the Eastern Cape we observed colour-ringed robins (n = 2) and thrushes (n = 2) on their breeding territory in all months of the year, suggesting that some individuals of both species are strongly resident.     

Effects of neonatal nutrition on adult reproduction in a passerine bird

Effects of neonatal nutrition on adult reproductive performance have been little studied. In Zebra Finches Taeniopygia guttata , poor neonatal nutrition is known to be associated with reduced blood antioxidant levels in adulthood, which could impair reproductive performance. Here, we compare the effects of standard-quality (SQ) or lower-quality (LQ) neonatal nutrition on components of fecundity. Compared with controls, LQ birds took longer to initiate egg-laying, and then laid eggs at a slower rate. LQ birds did not, however, show reduced clutch mass or size, or yolk antioxidant levels (retinol; α- or γ-tocopherol; carotenoids). Zebra Finches breed opportunistically, often only once in their short lifetime. Therefore, the timing but also the number and quality of eggs are critical fitness-related traits. Our results indicate that LQ birds had impaired reproductive capacity, suggesting resource accumulation constraints. Maximizing egg number and quality appears to have been more important than rapid egg production.