Barsova, L.I., Soldatova, I.B., Kirjanovskaja, N.V. & Golubeva, T.B. 1998. Development of brainstem auditory nuclei and hearing sensitivity. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr. Durban, University of Natal. Ostrich 69: 387.

Six stages of neuronal development in three auditory nuclei of medulla oblongata (n. magnocellularus, n. angularis, and n. laminaris) were defined in Nissle-stained preparations and the correlation of these stages with the development of hearing sensitivity was established in ontogeny of Gallus gallus , Larus argentatus, Corvus cornix, Pica pica, and Ficedula hypoleuca. The neurons pass from the stage of undifferentiated neuroblast to stage of early growth when cochlear microphonic is first recorded. Neurons grow rapidly with the onset of intensive stage of hearing development, which begins with the onset of the young's own vocalisation. Neurons in the stage of late growth are believed to be related with the acoustical imprinting. During the period of eyes opening the rostro-caudal growth of the auditory nuclei is characterised by a delay matching the delay in the development of hearing. Neurons grow at the highest rate at the rostral level of n.magnocellularis. The curve of linear growth of auditory nuclei is similar with the growth curve of the neurons and follows Bertalanffy's equation. The growth of neurons and increase of the size of auditory nuclei continue at least until puberty.

Key words: ontogeny, auditory nuclei, morphology, neurons, auditory sensitivity

 

Brown, C.R. & Brown, M.B. 1998. Intense natural selection on body size among swallows during severe weather. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr. Durban, University of Natal. Ostrich 69: 388.

Extreme climatic disturbances provide excellent opportunities to study natural selection in wild populations, sometimes causing directional shifts in character traits. Insectivorous Cliff Swallows Hirundo pyrrhonota and Barn Swallows Hirundo rustica in the northern USA must often endure periods of cold weather in late spring that reduce food availability. If cold spells last four or more days, mortality due to starvation may result. We analyse morphological shifts associated with viability selection, and how patterns of fluctuating asymmetry (FA) were affected by survival selection, during periods of cold weather in 1992 and 1996 in southwestern Nebraska. Birds that died during the cold were compared to those still alive when the severe weather ended. The more severe cold spell in 1996 killed thousands of Cliff Swallows; comparable mortality events occurred in only one other year since 1875. Among both species, larger birds as measured by geometric mean body size were favoured in both events. Tarsus length, culmen width and length, and wing length were targets of selection in 1996. Survivors had lower wing and tail FA in both events, and wing and tail FA were targets of selection in Cliff Swallows. In Barn Swallows, neither measure of FA was a target of selection. Larger swallows were probably favoured in cold weather due to the thermal advantages of large size and the ability to store more fat.

Key words: Barn Swallow, Cliff Swallow, climate, fluctuating asymmetry, Hirundo rustica, Hirundo pyrrhonota, survival

 

Gussekloo, S.W.S & Zweers, G.A. 1998. Cranial kinesis in paleognathous birds. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr. Durban, University of Natal. Ostrich 69: 389.

The Paleognathae form a group of birds whose position in evolution and systematics has caused more dispute than that of any other group of birds. One of the most important characters by which Paleognathae are identified is the structure of the palatal complex. Another character, found only in Paleognathae, is central rhynchokinesis in the upper jaw. The palatal complex in neognathous birds plays a crucial role in the cranial kinesis and therefore in jaw motion and feeding. In this paper we analyse the function of the structure of the paleognathous palate in combination with central kinesis in feeding mechanisms and its evolutionary importance. Video analyses of feeding Paleognathae were used to study central kinesis and X-ray photogrammetry was used to determine the three-dimensional movement of the elements of the palatal complex during kinesis. Force experiments were carried out to measure the required force necessary for kinesis. These results were compared with muscle force values obtained from a model. Experimental results show that kinesis is possible and that sufficient strength for kinesis can be produced. However, kinesis has not been observed in feeding behaviour. Based on these functional results a new evolutionary pathway is hypothesised in which both the palatal structure and scaling in the Paleognathae are channelling factors.

Key words: Paleognathae, photogrammetry, cranial kinesis, evolution, palatal complex

 

Hille, S.M. & Winkler, H. 1998. Sexual dimorphism among island populations of the Kestrel on Cape Verde. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr. Durban, University of Natal. Ostrich 69: 389.

Islands are the field laboratory of evolutionary scientists because they offer geographically separated populations, which are subject to several evolutionary forces like genetic bottle-necks, drift, gene-flow and locally divergent environments. On the Cape Verde Islands, two allopatric taxa of the Kestrel, Falco tinnunculusneglectus (SCHLEGEL, 1873) and Falco tinnunculus alexandrii (BOURNE, 1955), are found. Individuals on different islands were measured and both kestrels show a sexual dimorphism in size which increases across the archipelago from the western to the eastern islands and goes along with an increase in intersexual difference of coloration. The kestrels on the easternmost islands resemble the European Kestrel Falco t. tinnunculus, a rare visitor to the islands. Individuals of the western populations are less different in size, but there exists a dimorphism in the shape of the trophic structures (legs, feet and bill). The origin of sexual dimorphism in size and in trophic structures among the island populations of the Kestrel on the archipelago will be discussed in relation to existing theories on ecological sexual dimorphism.

Key words: sexual dimorphism, ecomorphology, kestrel, island populations, adaptive divergence

 

Hofling, E. 1998. Comparative cranial anatomy of Ramphastidae and Capitonidae. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr. Durban, University of Natal. Ostrich 69: 389.

Recent research suggest that Neotropical Capitonidae are closer to Ramphastidae than to Old World Capitonidae. The present research, based on cranial osteology, aims to further contribute to this discussion. The cranial anatomy of 19 species of Ramphastidae and seven species of Neotropical, Ethiopian, and Oriental Capitonidae was studied. Among the most relevant findings is the fact that Pteroglossus, Baillonius, Selenidera, and Aulacorhynchus present a lacrimal apophysis, as observed in Semnornis ramphastinus, and Capito niger. The post-orbital process develops to different degrees in all species and, contrary to what is stated in the literature, the post-orbital ligament is also present in Ramphastos tucanus, R. dicolorus, and R. vitellinus. The palate in Capitonidae is different from the one found in Ramphastidae, presenting, among other features, a bifurcated vomer, and interpalatine and transpalatine processes. The most variable aspects of the upper jaw, besides its dimension and shape, are the nasal openings and the frontonasal suture. The genus Ramphastos is the only one that presents an osseous lamina separating the post-nasal foramen from the external nares. In the remaining species studied, both from Ramphastidae and Capitonidae, there exists an osseous depression where this foramen is located.

Key words: anatomy, Ramphastidae, Capitonidae, cranial, osteology

 

Homberger, D.G. & de Silva, K.N. 1998. The role of cutaneous and subcutaneous fat in the mechanism of feather movement. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr. Durban, University of Natal. Ostrich 69: 390.

The skin of birds, unlike that of other vertebrates, contains a lot of fat. A microanatomical study of the domestic turkey revealed that this fat plays a crucial role in the biomechanics of feather movement. It is stored in two layers that are separated by an elastic lamina: the dermis surrounding the feather follicles and smooth feather muscles, and the subcutaneous Fascia superficialis. When erector feather muscles contract, the feather follicles rotate into a more vertical position and push against the underlying fascia. The hydraulic fascia bulges between the compression points created by the feather follicles as it maintains a constant volume, and the elastic lamina between the dermis and the fascia is stretched. When erector feather muscles relax or depressor feather muscles contract, the feather follicles rotate into a more horizontal position and release the pressure on the fascia, and the resilient elastic lamina flattens the fascial bulges between the feather follicles. This biomechanical model of feather movement forms the basis for studies of more specialised motions of feathers for flight, thermoregulation, and communication.

Key words: skin, lipids, biomechanics, plumage, adaptation

 

Johansson, C.L. & Norberg, U.M. 1998. Morphology of the legs of swimming birds in relation to swimming behaviour. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr. Durban, University of Natal. Ostrich 69: 390.

The structure and function of the legs and feet of swimming birds are closely related to the way they exploit their environment. Swimming behaviour, including speed, force production and manoeuverability is closely linked to body, leg and foot morphology. I did an eco-morphological study, based on data on foot-area and on the length of the femur, the tibiotarsus, the tarsometatarsus and the first phalanx of the third toe of 40-42 species of swimming and diving birds. Multivariate analysis and least-squares regression were used to trace similarities and dissimilarities among birds of different size and with different swimming behaviour. Foot area and the length of the first phalanx of the third toe increase faster (P < 0.01), and the length of the femur increase slower (P < 0.05), with increasing body size than expected from isometry. This suggests that larger birds move a proportionally larger amount of water in a power stroke, than do small birds. This may be related to the lower foot stroke frequency observed in larger birds.

Key words: morphometrics, seabird, eco-morphology, wader, diving

 

Kolsch, M., Blaehser, S. & Tasch, S. 1998. Neuropeptidergic fibers correlating avian vocal control and respiratory systems. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr. Durban, University of Natal. Ostrich 69: 391.

Song is a complex behaviour-pattern regulated by the vocal control system (VCS). The morphological substrate consists of interconnected nuclei, e.g. the High Vocal Center (HVC), Nc. robustus archistriatalis (RA), Area X, some thalamic nuclei, Nc. intercollicularis (Ico), and Nc. nervi hypoglossi, pars tracheosyringealis (XIIts). The vocal activity is associated with the respiratory system (RS). Most birds produce song during pulsed expiration. Therefore the functional circuits of VCS and RS are linked centrally. Ico is related to both circuits: by descending afferents from RA receiving inputs from HVC, and by afferents from Nc. parabrachialis and Nc. retroambiguus of the RS. The Ico itself projects to XIIts, controlling the syrinx. To determine peptidergic afferents in both circuits, brains of Zebra Finches and domestic chickens were embedded in paraffin, sectioned serially, and marked with antisera against several neuropeptides. The results show neuropeptidergic afferents for Vasoactive Intestinal Polypeptide (VIP), Methionine-enkephalin (ME), Substance P (SP), and Neuropeptide Y (NPY) in VCS. Immunoreactivity for these peptides is detected in Ico with high SP density. Nc. parabrachialis is immunopositive for SP, ME, VIP and NPY. The high density of immunopositive fibers in Ico and Nc. parabrachialis points to neuropeptidergic involvement in the regulation of respiratory control during vocalisation.

Key words: Taeniopygia guttata, neuropeptides, song control

 

Lei, F-m. & Yin, Z-H. 1998. Adaptation to terrestrial life and geographical variation of the Little Owl Athene noctua in China. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr.. Durban, University of Natal. Ostrich 69: 392.

The Little Owl Athene noctua has differentiated in four subspecies in large areas of northern China. The paper interprets how the birds are adapted to their terrestrial life and different geographical environment on basis of behavioral and comparative morphological analysis. The soft and elongated barbules of feathers and fringed remises are well adapted to their nocturnal life. The longer legs of the Little Owl (0.88) than that of the Long-eared Owl Asio otus (0.79) and Eagle Owl (0.78), and the specific comic-bobbing behavior suggest that they are potentially more active on the ground. Among the four subspecies, A. n. ludlowi, has the darkest body coloration, longest winglength and middle claw of left foot and is distributed in the colder, much more windy and high-altitude areas of Xizang Plateau. A. n. orientalis inhabitants the very arid and desert regions in Xinjiang. It is the palest race of the races in China. Specimens from Gansu and Qinghai Provinces are intermediate between the two subspecies, whereas those from northern areas and the northwestern part of the Inner Mongolia, are intermediate between A. n. plumipes and A. n. impasta is intermediate between A. n. ludlowi and A.n. plumipes in body coloration as well as in wing length and the claw length. All variations above among the four races are clinal.

Key words: Athene noctua, China, clinal variation, morphology, terrestrial adaptations

 

Neubert, I. & Blaehser, S. 1998. Cytoarchitectural organisation of the dorsal vagal complex in Gallus gallus. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr. Durban, University of Natal. Ostrich 69: 393.

The dorsal vagal complex (DVC) is located in the dorsal medulla oblongata, consisting of the Area postrema, and two major longitudinal cell columns, i.e. the viscero-sensory nucleus of the solitary tract (NTS) and the parasympathetic dorsal motor nucleus of the vagus nerve (DMNX). The complex provides part of the vagal innervation of the upper gastrointestinal tract, trachea, bronchi, lungs and heart. It contains dense fiber projections of various neuropeptides, each with a unique spatial distribution. We tried to correlate this distribution with different morphological divisions. The description of the cytoarchitecturally different subnuclei is based on studies of Nissl-stained, paraffin-embedded brain sections of adult male chickens. Neurons were classified on morphological features: size, form, staining characteristics, and location. It was possible to define 14 distinct subnuclei within NTS: rostral to the obex seven medial and four lateral to the Tractus solitarius; three subdivisions caudal to the obex. The DMNX could be subdivided into nine subnuclei: three caudal and six rostral to the obex. The analysed cytoarchitectural organisation of the DVC indicates functional relationships between subpopulations of vagal neurons and their specific involvement in the generation, regulation and co-ordination of various catecholaminergically and neuropeptidergically coded reflex-circuits.

Key words: Gallus domesticus, dorsal vagal complex, cytoarchitecture

 

Posso, S.R. 1998. Cranial osteology in Coccyzidae, Opisthocomidae, Crotophagidae and Neomorphidae. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr. Durban, University of Natal. Ostrich 69: 393.

The Coccyzidae, Opisthocomidae, Crotophagidae and Neomorphidae are families of Cuculiformes found mainly in the Neotropical region. Osteological studies on these groups must be re-evaluated because few species were used and many characters were not described. Thus, a more detailed study on osteology of the Neotropical Cuculiformes is missing. The goal of this study was to describe the cranial osteology of the species within each group. Thirteen species and 24 skulls of the Neotropical Cuculiformes were examined for this study. Crotophaga ani was used as the pattern on which osteological descriptions were based. There are many differences among the species of the three families and the Opisthocomidae. The latter is the most divergent group among these families and might be placed in a distinct taxon. Coccygidae, Crotophagidae and Neomorphidae share many cranial osteological characteristics.

Key words: osteology, skull, Cuculiformes, Neotropical

 

Zhang, Y.H., Lei, F.M. & Yin, Z.H. 1998. Comparative studies on retina structure of Bubo bubo, Athene noctua and Falco tinnunculus. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr.. Durban, University of Natal. Ostrich 69: 394.

The thickness of each layer, the layer number of nucleus and the photoreceptor density in retinas of Bubo bubo, Athene noctua and Falco tinnunculus were observed, measured and counted by LM and SEM, for studying the ecomorphological features on basis of their retina structures and habits. The layer numbers of outer and inner layers and ganglion cell layer are separately 2.6, 17.6 and 0.4 in B. bubo; 3.0, 14.1 and 1.9 in A. noctua; 1.6, 14.6 and 1.7 in F. tinnunculus respectively. The cone densities in central area of retina are 190117 ± 27304 mm², 202122 ± 49542 mm² and 234039 ± 44916 mm² respectively besides cone's distribution in retinal periphery of F. tinnunculus. The rod densities in peripheral area of retina are 190422 ± 26595 mm², 165800 ± 26408mm² and 178015 ± 40165 mm² respectively. They are found in the same habitats in Qishan County, Shaanxi Province, but have different daily activity rhythms. That the retina structures are closely related with their activity patterns, and suggest that the structure base could facilitate nocturnality of the former two species and diurnality of F. tinnunculus, and that the retina structure of A. noctua is well suitable to its specialised crepuscular activity.

Key words: retina structure, habitat, adaptation, terrestrial life, geographical variation

 

Zueva, L.V., Chochlova, T.V., Korneeva, E.V. & Golubeva, T.B. 1998. Development of retina is related to visually-guided behaviour in Pied Flycatcher nestlings Ficedula hypoleuca. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr.. Durban, University of Natal. Ostrich 69: 394.

In Pied Flycatcher nestling begging is induced by acoustic signals after hatching and by visual stimulation after eyes opening. Begging is induced on day 5-6 by the change in luminosity caused by parent flying through the entrance-hole, and on day 9-10 the bird's silhouette becomes an additional stimulus and by day 13 vision is the leading sensory stimulus. It is suggested that the involvement of vision into the organisation of behaviour is limited by the degree of maturity of retinal cells. The development of retina was studied in 1-14 day-old nestlings by light and electron microscopy. To investigate the development of retinal topology, oil droplets of cones in the fresh whole-mount preparations were used. Oil droplets form in the distal part of the cone's inner segment just before the onset of the light sensitive outer segment development. The first oil drops (red, yellow and then colourless) are found locally in the temporal fovea of 6-day-old nestlings. On day 7, the droplets appear in the central fovea, while synapses look more mature in the temporal fovea. Their number increases, and on day 9 temporal and foveal droplet-containing regions merge. On day 13-14 whole retina has colour oil drops and mature photoreceptors cells. This study was supported by RFBR grant # 97-04-49581

Key words: begging, vision, retina, oil droplets, ontogeny