Comparison Of Birds Research Articles

A classification scheme for scoring subcutaneous fat depots of shorebirds

Different scoring systems have been developed for assessing fat stores in birds. Most have been used with passerines, and there is no widely used standard for studies of shorebirds. I developed a new fat-scoring classification scheme for shorebirds that was tested in Poland with juvenile Dunlins {Calidris alpina) during autumn and Wood Sandpipers ( Tringa glareola) during spring migration. My proposed fatness scale is based on a qualitative assessment of the amount of fat in the axillary region and, if necessary, the furcular region. The resulting fat scores do not predict the actual amount of fat carried by a bird, but can be used to assign birds to a particular state of fatness and allow comparison of birds with different scores. Analysis revealed that the relationship between fat scores and predicted fat mass was approximately linear for both Dunlins and Wood Sandpipers. Although the scale I propose was tested with 20 species of shorebirds, sample sizes for larger species were small and consisted exclusively of lean and moderately fat birds. As a result, my proposed fat-scoring system should be evaluated using larger and fatter shorebirds because it has only been validated for one small and one medium-sized species.

Photoperiodic induced changes in reproductive state of border canaries ( Serinus canaria) are associated with marked variation in hypothalamic gonadotropin-releasing hormone immunoreactivity and the volume of song control regions

In temperate zone songbirds, such as canaries ( Serinus canaria), seasonal variation in gonadal activity and behavior are associated with marked brain changes. These include gonadotropin-releasing hormone (GnRH) expression and the volume of brain areas controlling song production. Questions have been raised about the consistency of seasonal brain changes in canaries. Laboratory studies of the American singer strain raised doubts as to whether this strain exhibits a robust photoperiodic response along with changes in brain GnRH content, and studies of free-living canaries have failed to identify seasonal changes in volume of song control nuclei. We assessed differences in brain GnRH and the song control system associated with photoperiod-induced variation in reproductive state in Border canaries. We found that males and females maintained for 10 weeks on long days (14L:10D) regress their gonads, exhibit a decline in testosterone and initiate molt; a response consistent with the onset of absolute photorefractoriness (i.e., failed to respond to previously stimulating daylengths). All birds regained photosensitivity (i.e., exhibited gonadal response to stimulating daylengths) after experiencing short days (8L:16D) for 6 weeks. Furthermore, comparisons of birds in either a photosensitive, photostimulated, or photorefractory state revealed a marked increase in GnRH protein expression in the photosensitive and photostimulated birds over photorefractory birds. A similar variation was observed in the volume of key forebrain song nuclei. Thus, Border canaries demonstrate measurable neuroplasticity in response to photoperiodic manipulations. These data, along with previous work on other strains of canaries, indicate the presence of intra-specific variation in photoperiodically regulated neuroplasticity.

Neuroanatomy of flying reptiles and implications for flight, posture and behaviour.

Comparison of birds and pterosaurs, the two archosaurian flyers, sheds light on adaptation to an aerial lifestyle. The neurological basis of control holds particular interest in that flight demands on sensory integration, equilibrium, and muscular coordination are acute. Here we compare the brain and vestibular apparatus in two pterosaurs based on high-resolution computed tomographic (CT) scans from which we constructed digital endocasts. Although general neural organization resembles birds, pterosaurs had smaller brains relative to body mass than do birds. This difference probably has more to do with phylogeny than flight, in that birds evolved from nonavian theropods that had already established trends for greater encephalization. Orientation of the osseous labyrinth relative to the long axis of the skull was different in these two pterosaur species, suggesting very different head postures and reflecting differing behaviours. Their enlarged semicircular canals reflect a highly refined organ of equilibrium, which is concordant with pterosaurs being visually based, aerial predators. Their enormous cerebellar floccular lobes may suggest neural integration of extensive sensory information from the wing, further enhancing eye- and neck-based reflex mechanisms for stabilizing gaze.

Trans-Beringia Comparisons of Mitochondrial DNA Differentiation in Birds

We compared mitochondrial DNA (mtDNA) restriction fragment profiles from samples of 13 bird species that occur on both sides of Beringia. All but two species, Lapland Longspur (Calcarius lapponicus) and Green-winged Teal (Anas crecca), exhibited evidence of genetic differentiation, albeit at varying degrees. Several species exhibited mtDNA differentiation consistent with species-level distinctness: Marbled Murrelet (Brachyramphus marmoratus), Three-toed Woodpecker (Picoides tridactylus), Whimbrel (Numenius phaeopus), Mew Gull (Larus canus), Black-billed Magpie (Pica pica), American Pipit (Anthus rubescens), and Rosy Finch (Leucosticte arctoa). Other species exhibited levels of mtDNA differentiation intermediate between populations and species: Barn Swallow (Hirundo rustica), Common Tern (Sterna hirundo), Common Snipe (Gallinago gallinago), and Pelagic Cormorant (Phalacrocorax pelagicus). Because of small sample sizes, we do not recommend formal taxonomic changes, although our data could be combined with other data to raise several taxa to species level. Our data do not indicate a consistent level of mtDNA differentiation between putatively conspecific populations on different sides of Beringia, suggesting different times of colonization or cessation of gene exchange. Most comparisons of birds within continents exhibit less mtDNA differentiation than our trans-Beringia comparisons, suggesting limited gene flow between continents.

Comparison of barometric and pneumotachographic measurements of resting ventilation in the little penguin ( Eudyptula minor)

1. 1. We compared the use of the barometric method and pneumotachography for measurement of ventilation in the little penguin Eudyptula minor. 2. 2. Simultaneous use of both techniques showed the barometric method to give a reliable estimate of tidal volume. 3. 3. Comparison of birds with and without masks for pneumotachography showed wearing masks to produce a significant increase in ventilation, principally through a raised respiratory frequency.

Cooperative breeding by the Gal�pagos mockingbird, Nesomimus parvulus

The costs and benefits of helping behavior were analyzed for 36 pairs of the Galapagos mockingbird, Nesomimus parvulus, and their associates. Helping at the nest is usually done by sons or males suspected to be offspring of the breeders. Costs and benefits to breeders were assessed by comparison of pairs with and without helpers, and costs and benefits to helpers were assessed by comparison of birds which help and those which establish themselves as novice breeders.