Optical Imaging of Retinotopic Maps in a Small Songbird,the Zebra Finch

Background

The primary visual cortex of mammals is characterised by a retinotopic representation of the visual field. It has therefore been speculated that the visual wulst, the avian homologue of the visual cortex, also contains such a retinotopic map. We examined this for the first time by optical imaging of intrinsic signals in zebra finches, a small songbird with laterally placed eyes. In addition to the visual wulst, we visualised the retinotopic map of the optic tectum which is homologue to the superior colliculus in mammals.

Methodology/Principal Findings

For the optic tectum, our results confirmed previous accounts of topography based on anatomical studies and conventional electrophysiology. Within the visual wulst, the retinotopy revealed by our experiments has not been illustrated convincingly before. The frontal part of the visual field (0°±30° azimuth) was not represented in the retinotopic map. The visual field from 30°–60° azimuth showed stronger magnification compared with more lateral regions. Only stimuli within elevations between about 20° and 40° above the horizon elicited neuronal activation. Activation from other elevations was masked by activation of the preferred region. Most interestingly, we observed more than one retinotopic representation of visual space within the visual wulst, which indicates that the avian wulst, like the visual cortex in mammals, may show some compartmentation parallel to the surface in addition to its layered structure.

Conclusion/Significance

Our results show the applicability of the optical imaging method also for small songbirds. We obtained a more detailed picture of retinotopic maps in birds, especially on the functional neuronal organisation of the visual wulst. Our findings support the notion of homology of visual wulst and visual cortex by showing that there is a functional correspondence between the two areas but also raise questions based on considerable differences between avian and mammalian retinotopic representations.     

Features of the Retinotopic Representation in the Visual Wulst of a Laterally Eyed Bird,the Zebra Finch (Taeniopygia guttata)

The visual wulst of the zebra finch comprises at least two retinotopic maps of the contralateral eye. As yet, it is not known how much of the visual field is represented in the wulst neuronal maps, how the organization of the maps is related to the retinal architecture, and how information from the ipsilateral eye is involved in the activation of the wulst. Here, we have used autofluorescent flavoprotein imaging and classical anatomical methods to investigate such characteristics of the most posterior map of the multiple retinotopic representations. We found that the visual wulst can be activated by visual stimuli from a large part of the visual field of the contralateral eye. Horizontally, the visual field representation extended from -5° beyond the beak tip up to +125° laterally. Vertically, a small strip from -10° below to about +25° above the horizon activated the visual wulst. Although retinal ganglion cells had a much higher density around the fovea and along a strip extending from the fovea towards the beak tip, these areas were not overrepresented in the wulst map. The wulst area activated from the foveal region of the ipsilateral eye, overlapped substantially with the middle of the three contralaterally activated regions in the visual wulst, and partially with the other two. Visual wulst activity evoked by stimulation of the frontal visual field was stronger with contralateral than with binocular stimulation. This confirms earlier electrophysiological studies indicating an inhibitory influence of the activation of the ipsilateral eye on wulst activity elicited by stimulating the contralateral eye. The lack of a foveal overrepresentation suggests that identification of objects may not be the primary task of the zebra finch visual wulst. Instead, this brain area may be involved in the processing of visual information necessary for spatial orientation.     

Diet of breeding Eleonora's falcon Falco eleonorae in Algeria: Insights for the autumn trans‐Mediterranean avian migration

How environmental changes are affecting bird population dynamics is one of the most challenging conservation issues. Dietary studies of top avian predators could offer scope to monitor anthropogenic drivers of ecosystem changes. We investigated the diet of breeding Eleonora''s falcon in an area of Northeastern Algeria in the years 2010–2012. Feathers and insect remains originating from prey plucking behavior were analyzed, providing insights into the seasonally changing diet of this raptor, as well as the trans‐Mediterranean avian migration. A total of 77 species of birds (16 Sylviidae, 11 Turdidae, and 4 Emberizidae), 3 species of insects, and 1 lizard were identified among prey remains, reflecting a diverse diet. Diet composition and prey abundance varied seasonally, faithfully correlating with the passage of migrant birds as recorded from bird ring recoveries. Our findings suggest that dietary studies of predators might be deployed to investigate changes in bird migration. We discuss our results in the context of trans‐Mediterranean migration, with early‐season prey mainly comprising trans‐Saharan migrants (Apus apus and Merops apiaster) and late‐season prey being dominated by Mediterranean winter migrants (Erithacus rubecula, Turdus philomelos, Sylvia atricapilla, and Sturnus vulgaris). Notably, we observed a significant reduction in species richness of passerine remains in 2012, potentially highlighting a decline in the diversity of avian migrants.     

Flavoprotein Autofluorescence Imaging of Visual System Activity in Zebra Finches and Mice

Large-scale brain activity patterns can be visualized by optical imaging of intrinsic signals (OIS) based on activity-dependent changes in the blood oxygenation level. Another method, flavoprotein autofluorescence imaging (AFI), exploits the mitochondrial flavoprotein autofluorescence, which is enhanced during neuronal activity. In birds, topographic mapping of visual space has been shown in the visual wulst, the avian homologue of the mammalian visual cortex by using OIS. We here applied the AFI method to visualize topographic maps in the visual wulst because with OIS, which depends on blood flow changes, blood vessel artifacts often obscure brain activity maps. We then compared both techniques quantitatively in zebra finches and in C57Bl/6J mice using the same setup and stimulation conditions. In addition to experiments with craniotomized animals, we also examined mice with intact skull (in zebra finches, intact skull imaging is not feasible probably due to the skull construction). In craniotomized animals, retinotopic maps were obtained by both methods in both species. Using AFI, artifacts caused by blood vessels were generally reduced, the magnitude of neuronal activity significantly higher and the retinotopic map quality better than that obtained by OIS in both zebra finches and mice. In contrast, our measurements in non-craniotomized mice did not reveal any quantitative differences between the two methods. Our results thus suggest that AFI is the method of choice for investigations of visual processing in zebra finches. In mice, however, if researchers decide to use the advantages of imaging through the intact skull, they will not be able to exploit the higher signals obtainable by the AFI-method.     

Avian brain evolution: new data from Palaeogene birds (Lower Eocene) from England

Investigation of how the avian brain evolved to its present state is informative for studies of the theropod–bird transition, and as a parallel to mammalian brain evolution. Neurological anatomy in fossil bird species can be inferred from endocranial casts, but such endocasts are rare. Here, we use computed tomographic analysis to determine the state of brain anatomy in two marine birds from the Lower Eocene London Clay Formation of England. The brains of Odontopteryx (Odontopterygiformes) and Prophaethon (Pelecaniformes) are remarkably similar to those of extant seabirds, and probably possessed similar somatosensory and motor capabilities. Each virtual endocast exhibits a degree of telencephalic expansion comparable to living avian species. However, the eminentia sagittalis (wulst), a feature characteristic of all living birds, is poorly developed. Our findings support the conclusion that much of the telencephalic expansion of modern birds was complete by the end of the Mesozoic, but that overall telencephalic volume has increased throughout the Cenozoic through dorsal expansion of the eminentia sagittalis. We suggest that improvements in cognition relating to telencephalic expansion may have provided neornithine avian clades with an advantage over archaic lineages at the Cretaceous–Tertiary boundary, explaining their survival and rapid diversification in the Cenozoic. © 2009 The Natural History Museum. Journal compilation © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 198–219.     

Relative Roles of Grey Squirrels,Supplementary Feeding,and Habitat in Shaping Urban Bird Assemblages

Non-native species are frequently considered to influence urban assemblages. The grey squirrel Sciurus carolinensis is one such species that is widespread in the UK and is starting to spread across Europe; it predates birds’ nests and can compete with birds for supplementary food. Using distance sampling across the urbanisation intensity gradient in Sheffield (UK) we test whether urban grey squirrels influence avian species richness and density through nest predation and competition for supplementary food sources. We also assess how urban bird assemblages respond to supplementary feeding. We find that grey squirrels slightly reduced the abundance of breeding bird species most sensitive to squirrel nest predation by reducing the beneficial impact of woodland cover. There was no evidence that grey squirrel presence altered relationships between supplementary feeding and avian assemblage structure. This may be because, somewhat surprisingly, supplementary feeding was not associated with the richness or density of wintering bird assemblages. These associations were positive during the summer, supporting advocacy to feed birds during the breeding season and not just winter, but explanatory capacity was limited. The amount of green space and its quality, assessed as canopy cover, had a stronger influence on avian species richness and population size than the presence of grey squirrels and supplementary feeding stations. Urban bird populations are thus more likely to benefit from investment in improving the availability of high quality habitats than controlling squirrel populations or increased investment in supplementary feeding.     

若尔盖湿地水鸟资源季节变化

若尔盖湿地位于青藏高原东缘,是我国最大的高寒泥炭湿地之一。2010年从3月至12月,对若尔盖湿地水鸟种类、数量和分布进行了较为系统的调查。共记录到48种26 050只水鸟,隶属于6目12科,其中雁鸭类水鸟最多,共统计到21 408只,占水鸟总数的82.2%。3月和10月是若尔盖湿地水鸟数量的高峰期;11月是低谷期,主要是由于水鸟的迁离和越冬水鸟尚未到达的缘故。尕海是若尔盖湿地的重要组成部分,全年物种数和水鸟数量占了整个若尔盖湿地较大的比例。卫星跟踪的结果表明,青海湖斑头雁(Anser indicus)在若尔盖湿地与云南和贵州的越冬水鸟汇合,因此加强若尔盖湿地禽流感的防控是非常重要的。     

Brain regions associated with visual cues are important for bird migration

Long-distance migratory birds have relatively smaller brains than short-distance migrants or residents. Here, we test whether reduction in brain size with migration distance can be generalized across the different brain regions suggested to play key roles in orientation during migration. Based on 152 bird species, belonging to 61 avian families from six continents, we show that the sizes of both the telencephalon and the whole brain decrease, and the relative size of the optic lobe increases, while cerebellum size does not change with increasing migration distance. Body mass, whole brain size, optic lobe size and wing aspect ratio together account for a remarkable 46% of interspecific variation in average migration distance across bird species. These results indicate that visual acuity might be a primary neural adaptation to the ecological challenge of migration.     

Local sleep homeostasis in the avian brain: convergence of sleep function in mammals and birds?

The function of the brain activity that defines slow wave sleep (SWS) and rapid eye movement (REM) sleep in mammals is unknown. During SWS, the level of electroencephalogram slow wave activity (SWA or 0.5-4.5 Hz power density) increases and decreases as a function of prior time spent awake and asleep, respectively. Such dynamics occur in response to waking brain use, as SWA increases locally in brain regions used more extensively during prior wakefulness. Thus, SWA is thought to reflect homeostatically regulated processes potentially tied to maintaining optimal brain functioning. Interestingly, birds also engage in SWS and REM sleep, a similarity that arose via convergent evolution, as sleeping reptiles and amphibians do not show similar brain activity. Although birds deprived of sleep show global increases in SWA during subsequent sleep, it is unclear whether avian sleep is likewise regulated locally. Here, we provide, to our knowledge, the first electrophysiological evidence for local sleep homeostasis in the avian brain. After staying awake watching David Attenborough's The Life of Birds with only one eye, SWA and the slope of slow waves (a purported marker of synaptic strength) increased only in the hyperpallium--a primary visual processing region--neurologically connected to the stimulated eye. Asymmetries were specific to the hyperpallium, as the non-visual mesopallium showed a symmetric increase in SWA and wave slope. Thus, hypotheses for the function of mammalian SWS that rely on local sleep homeostasis may apply also to birds.     

Greater hippocampal neuronal recruitment in food-storing than in non-food-storing birds

Previous research has shown heightened recruitment of new neurons to the chickadee hippocampus in the fall. The present study was conducted to determine whether heightened fall recruitment is associated with the seasonal onset of food-storing by comparing neurogenesis in chickadees and a non-food-storing species, the house sparrow. Chickadees and house sparrows were captured in the wild in fall and spring and received multiple injections of the cell birth marker bromodeoxyuridine (BrdU). Birds were held in captivity and the level of hippocampal neuron recruitment was assessed after 6 weeks. Chickadees showed significantly more hippocampal neuronal recruitment than house sparrows. We found no seasonal differences in hippocampal neuronal recruitment in either species. In chickadees and in house sparrows, one-third of new cells labeled for BrdU also expressed the mature neuronal protein, NeuN. In a region adjacent to the hippocampus, the hyperpallium apicale, we observed no significant differences in neuronal recruitment between species or between seasons. Hippocampal volume and total neuron number both were greater in spring than in fall in chickadees, but no seasonal differences were observed in house sparrows. Enhanced neuronal recruitment in the hippocampus of food-storing chickadees suggests a degree of neurogenic specialization that may be associated with the spatial memory requirements of food-storing behavior.     

Fine‐scale impacts on avian biodiversity due to a despotic species,the bell miner (Manorina melanophrys)

Bell miners (Manorina melanophrys; Meliphagidae) are a highly social and very aggressive honeyeater. They are despotic and cooperate in the defence of their territories against other bird species, leading to the almost complete exclusion of other avifauna from miner‐occupied regions. This study aimed to resolve some of the fine‐scale effects of bell miner aggression on avian diversity both within and adjacent to colonies to determine the true impact of a colony on local avifaunal abundance. Three areas, distributed throughout the range of the bell miner, were surveyed across both non‐breeding and breeding seasons to assess the temporal and spatial impacts of bell miner aggression on other bird species. Bell miner colonies were found to occupy very clearly defined areas and had the expected negative impact on avian diversity within their colony. The effects of bell miner colony presence on abundance and richness of avian species were found to cease at the colony boundary, with both recovering to normal levels immediately outside the bell miner colony. Whether bell miners were breeding or not, and irrespective of the amount of vegetation coverage, bell miner colonies were found to have relatively marginal impacts on avian richness and abundance. No impact of colony presence/absence was found on the richness or abundance of the avian species that dwell in the undergrowth, with some evidence that these species were actually more common at the colony edge. Our results demonstrate that the influence of bell miner colony presence upon avian biodiversity is restricted to the confines of the colony and does not radiate outwards into the surrounding habitat. Colony presence influences, therefore, have implications when considering the impact of bell miner behaviour on the diversity of insectivorous birds and processes, most notably the propagation of Bell Miner Associated Dieback.     

Effect of Incubation on Bacterial Communities of Eggshells in a Temperate Bird,the Eurasian Magpie (Pica pica)

Inhibitory effect of incubation on microbial growth has extensively been studied in wild bird populations using culture-based methods and conflicting results exist on whether incubation selectively affects the growth of microbes on the egg surface. In this study, we employed culture-independent methods, quantitative PCR and 16S rRNA gene pyrosequencing, to elucidate the effect of incubation on the bacterial abundance and bacterial community composition on the eggshells of the Eurasian Magpie (Pica pica). We found that total bacterial abundance increased and diversity decreased on incubated eggs while there were no changes on non-incubated eggs. Interestingly, Gram-positive Bacillus, which include mostly harmless species, became dominant and genus Pseudomonas, which include opportunistic avian egg pathogens, were significantly reduced after incubation. These results suggest that avian incubation in temperate regions may promote the growth of harmless (or benevolent) bacteria and suppress the growth of pathogenic bacterial taxa and consequently reduce the diversity of microbes on the egg surface. We hypothesize that this may occur due to difference in sensitivity to dehydration on the egg surface among microbes, combined with the introduction of Bacillus from bird feathers and due to the presence of antibiotics that certain bacteria produce.     

Neuropeptide Y mRNA and peptide in the night-migratory redheaded bunting brain

This study investigated the distribution of neuropeptide Y (NPY) in the brain of the night-migratory redheaded bunting (Emberiza bruniceps). We first cloned the 275-bp NPY gene in buntings, with ≥95 % homology with known sequences from other birds. The deduced peptide sequence contained all conserved 36 amino acids chain of the mature NPY peptide, but lacked 6 amino acids that form the NPY signal peptide. Using digosigenin-labeled riboprobe prepared from the cloned sequence, the brain cells that synthesize NPY were identified by in-situ hybridization. The NPY peptide containing cell bodies and terminals (fibers) were localized by immunocytochemistry. NPY mRNA and peptide were widespread throughout the bunting brain. This included predominant pallial and sub-pallial areas (cortex piriformis, cortex prepiriformis, hyperpallium apicale, hippocampus, globus pallidus) and thalamic and hypothalamic nuclei (organum vasculosum laminae terminalis, nucleus (n.) dorsolateralis anterior thalami, n. rotundus, n. infundibularis) including the median eminence and hind brain (n. pretectalis, n. opticus basalis, n. reticularis pontis caudalis pars gigantocellularis). The important structures with only NPY-immunoreactive fibers included the olfactory bulb, medial and lateral septal areas, medial preoptic nucleus, medial suprachiasmatic nucleus, paraventricular nucleus, ventromedial hypothalamic nucleus, optic tectum, and ventro-lateral geniculate nucleus. These results demonstrate that NPY is possibly involved in the regulation of several physiological functions (e.g. daily timing feeding, and reproduction) in the migratory bunting.     

宁夏罗山国家级自然保护区鸟类区系特征及群落结构

自2010年10月至2011年12月对宁夏罗山国家级保护区鸟类区系及群落结构进行了调查研究,共记录到鸟类15目46科98属164种,占宁夏已知鸟类总种数的48.81%。其中留鸟51种(31.10%),夏候鸟68种(41.64%),旅鸟38种(23.17%),冬候鸟7种(4.27%)。繁殖鸟119种,其中以古北界鸟类占优势,有88种,占繁殖鸟总数的73.95%;东洋界种15种,占12.61%;广布种鸟类16种,占13.45%。研究发现不同季节、不同生境中的鸟类群落特征差异较大。林地鸟类物种数和多样性指数最高,水域鸟类具有最高的G-F指数。相似性分析显示,山地荒漠草地和废弃村庄的鸟类群落,林地和浅山灌丛鸟类群落,分别具有一定的相似性。春季鸟类群落物种数、G-F指数、多样性指数和均匀度指数最高。     

Quantitative trait locus analysis of Verticillium wilt resistance in an introgressed recombinant inbred population of Upland cotton

Verticillium wilt (VW) of Upland cotton (Gossypium hirsutum L.) is caused by the soil-borne fungal pathogen Verticillium dahlia Kleb. The availability of VW-resistant cultivars is vital for control of this economically important disease, but there is a paucity of Upland cotton breeding lines and cultivars with a high level of resistance to VW. In general, G. barbadense L. (source of Pima cotton) is more VW-resistant than Upland cotton. However, the transfer of VW resistance from G. barbadense to Upland cotton is challenging because of hybrid breakdown in the F2 and successive generations of interspecific populations. We conducted two replicated greenhouse studies (tests 1 and 2) to assess the heritability of VW resistance to a defoliating V. dahliae isolate and identify genetic markers associated with VW resistance in an Upland cotton recombinant inbred mapping population that has stable introgression from Pima cotton. Disease ratings at the seedling stage on several different days after the first inoculation (DAI) in test 1, as well as the percentages of infected and defoliated leaves at 2 DAI in test 2, were found to be low to moderately heritable, indicating the importance of a replicated progeny test in selection for VW resistance. With a newly constructed linkage map consisting of 882 simple sequence repeat, single nucleotide polymorphism, and resistance gene analog–amplified fragment length polymorphism marker loci, we identified a total of 21 quantitative trait loci (QTLs) on 11 chromosomes and two linkage groups associated with VW resistance at several different DAIs in greenhouse tests 1 and 2. The markers associated with the VW resistance QTLs will facilitate fine mapping and cloning of VW resistance genes and genomics-assisted breeding for VW-resistant cultivars.     

Migratory birds have higher prevalence and richness of avian haemosporidian parasites than residents

Individuals of migratory species may be more likely to become infected by parasites because they cross different regions along their route, thereby being exposed to a wider range of parasites during their annual cycle. Conversely, migration may have a protective effect since migratory behaviour allows hosts to escape environments presenting a high risk of infection. Haemosporidians are one of the best studied, most prevalent and diverse groups of avian parasites, however the impact of avian host migration on infection by these parasites remains controversial. We tested whether migratory behaviour influenced the prevalence and richness of avian haemosporidian parasites among South American birds. We used a dataset comprising ~ 11,000 bird blood samples representing 260 bird species from 63 localities and Bayesian multi-level models to test the impact of migratory behaviour on prevalence and lineage richness of two avian haemosporidian genera (Plasmodium and Haemoproteus). We found that fully migratory species present higher parasite prevalence and higher richness of haemosporidian lineages. However, we found no difference between migratory and non-migratory species when evaluating prevalence separately for Plasmodium and Haemoproteus, or for the richness of Plasmodium lineages. Nevertheless, our results indicate that migratory behaviour is associated with an infection cost, namely a higher prevalence and greater variety of haemosporidian parasites.     

Mapping Global Diversity Patterns for Migratory Birds

Nearly one in five bird species has separate breeding and overwintering distributions, and the regular migrations of these species cause a substantial seasonal redistribution of avian diversity across the world. However, despite its ecological importance, bird migration has been largely ignored in studies of global avian biodiversity, with few studies having addressed it from a macroecological perspective. Here, we analyse a dataset on the global distribution of the world’s birds in order to examine global spatial patterns in the diversity of migratory species, including: the seasonal variation in overall species diversity due to migration; the contribution of migratory birds to local bird diversity; and the distribution of narrow-range and threatened migratory birds. Our analyses reveal a striking asymmetry between the Northern and Southern hemispheres, evident in all of the patterns investigated. The highest migratory bird diversity was found in the Northern Hemisphere, with high inter-continental turnover in species composition between breeding and non-breeding seasons, and extensive regions (at high latitudes) where migratory birds constitute the majority of the local avifauna. Threatened migratory birds are concentrated mainly in Central and Southern Asia, whereas narrow-range migratory species are mainly found in Central America, the Himalayas and Patagonia. Overall, global patterns in the diversity of migratory birds indicate that bird migration is mainly a Northern Hemisphere phenomenon. The asymmetry between the Northern and Southern hemispheres could not have easily been predicted from the combined results of regional scale studies, highlighting the importance of a global perspective.     

Peripheral melatonin modulates seasonal immunity and reproduction of Indian tropical male bird Perdicula asiatica

Seasonal changes in pineal function are well coordinated with seasonal reproductive activity of tropical birds. Further, immunomodulatory property of melatonin is well documented in seasonally breeding animals. Present study elucidates the interaction of peripheral melatonin with seasonal pattern of immunity and reproduction in Indian tropical male bird Perdicula asiatica. Significant seasonal changes were noted in pineal, testicular and immune function(s) of this avian species. Maximum pineal activity along with high immune status was noted during winter month while maximum testicular activity with low immune status was noted in summer. During summer month's long photoperiod suppressed pineal activity and high circulating testosterone suppressed immune parameters, while in winter short photoperiod elevated pineal activity and high circulating melatonin maintained high immune status and suppressed gonadal activity. Therefore, seasonal levels of melatonin act like a major temporal synchronizer to maintain not only the seasonal reproduction but also immune adaptability of this avian species.     

Testosterone, paternal behavior, and aggression in the monogamous California mouse (Peromyscus californicus)

Testosterone (T) mediates a trade-off, or negative correlation, between paternal behavior and aggression in several seasonally breeding avian species. However, the presence or absence of a T-mediated trade-off in mammals has received less attention. We examined the relationship between paternal behavior and territorial aggression in the biparental California mouse, Peromyscus californicus. In contrast to seasonally breeding birds, T maintains paternal behavior in this year-round territorial species. Castration reduced paternal behavior, whereas T replacement maintained high levels of paternal behavior. We hypothesize that T is aromatized in the brain to estradiol, which in turn stimulates paternal behavior. In contrast to paternal behavior, aggressive behavior was not reduced by castration. Interestingly, only sham males showed an increase in aggression across three aggression tests, while no change was detected in castrated or T-replacement males. Overall, trade-offs between aggression and paternal behavior do not appear to occur in this species. Measures of paternal behavior and aggression in a correlational experiment were actually positively correlated. Our data suggest that it may be worth reexamining the role that T plays in regulating mammalian paternal behavior.     

A provisional checklist of the avifauna of Turaif province,the Kingdom of Saudi Arabia

The richness and diversity of avian species inhabiting Turaif province of Saudi Arabia were surveyed for a period of one-year (2014–2015) using walked belt transects in different habitats of the studied area. Bird species were observed and recorded by sightings or vocal calls. A total of thirty-three bird species belonging to fifteen families were observed across all the surveys in the Turaif area. During a breeding season, species abundance was higher as compared to non-breeding season. Out of 33, eighteen species were passage migrants and fifteen species were noted as breeding residents. Family Muscicapidae which showed the highest proportion (24.24%) was represented by 8 bird species followed by family Alaudidae and family Falconidae represented by 4 species each. According to this survey relatively a fair quantity of bird species still exists in the Turaif region. This area is of significant interest in terms of conservation of birds due to higher densities of endemic, breeding or resident avian species.