DOCSLIB.ORG

Evidence That Population Increase and Range Expansion by Eurasian

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Evidence That Population Increase and Range Expansion by Eurasian bioRxiv preprint doi: https://doi.org/10.1101/491522; this version posted July 25, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 1 Evidence that population increase and range expansion by 2 Eurasian Sparrowhawks has impacted avian prey populations 3 4 Christopher Paul Bell bioRxiv preprint doi: https://doi.org/10.1101/491522; this version posted July 25, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 2 5 Abstract 6 The role of increased predator numbers in the general decline of bird populations in the late 7 20th century remains controversial, particularly in the case of the Eurasian Sparrowhawk, for 8 which there are contradictory results concerning its effect on the abundance of potential 9 prey species. Previous studies of breeding season census data for Sparrowhawks and prey 10 species in Britain have measured predator abundance either as raw presence-absence data 11 or as an estimate derived from spatially explicit modelling, and have found little evidence of 12 association between predator and prey populations. Here, a predator index derived from 13 site-level binary logistic modelling was used in a regression analysis of breeding census data 14 on 42 prey species, with significant effects emerging in 27 species (16 positive, 11 negative). 15 The frequency of significant positive associations may indicate the tracking of prey 16 abundance by Sparrowhawks, which would tend to cancel out any negative predation effect 17 on prey populations, rendering it difficult to detect using census data. If so, the negative 18 effects that have emerged for some species may underestimate the impact of increased 19 Sparrowhawk numbers on the prey populations concerned. Nevertheless, estimates of the 20 effect on national populations of prey species, obtained by combining effect sizes with a 21 measure of the increase in site occupancy by the predator, suggest the possibility of a 22 substantial impact. It cannot, therefore, be ruled out that the increase in abundance and 23 range expansion of Sparrowhawks made a significant contribution to contemporaneous 24 declines in the populations of many of its prey species. 25 bioRxiv preprint doi: https://doi.org/10.1101/491522; this version posted July 25, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 3 26 Introduction 27 The marked population decline that occurred across a wide range of bird species in the 28 British Isles during the late 20th Century is an event of major conservation concern that 29 remains imperfectly understood. Consequently, it is still liable to generate controversy, 30 particularly over the possibility that increased predator populations may have played a role 31 (Gibbons et al. 2007, Roos et al. 2018). Declines occurred chiefly among songbirds, of which 32 the major predator in western Europe is the Eurasian Sparrowhawk Accipiter nisus 33 (henceforth ‘Sparrowhawk’), a species that increased rapidly in range and abundance during 34 the same period, following a pesticide-related crash in the 1940s and 50s (Newton 1986). 35 The main source of evidence for population declines in Britain is the Common Birds Census 36 (CBC), which ran from 1962 to 2000, and involved intensive field survey designed to 37 estimate the number of breeding territories in a census plot (Marchant 1983). Previous 38 analyses of CBC data have concluded that there is little evidence for any connection 39 between increased Sparrowhawk numbers and songbird population declines (Thomson et 40 al. 1998, Newson et al. 2010), but analyses of data from another census scheme, the Garden 41 Bird Feeding Survey (GBFS), have consistently found evidence of a negative association 42 between Sparrowhawks and House Sparrows (Bell et al. 2010, Swallow et al. 2015, 2016, 43 Jones-Todd 2018). 44 GBFS data is derived from weekly maximum counts made at bird feeding stations over the 45 winter months (Chamberlain et al. 2005), which can be averaged to derive an annually 46 varying index of species abundance, with that for Sparrowhawk being effectively the 47 proportion of weeks during which attacks on a feeding station were observed. The GBFS- 48 derived Sparrowhawk index may thus be taken to be a continuous measure of predation bioRxiv preprint doi: https://doi.org/10.1101/491522; this version posted July 25, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 4 49 pressure at a point location, resulting in commensurate declines in the use of the feeder at 50 that location by potential prey species. CBC data are recorded during the breeding season, 51 and refer to a much wider area, typically 20-150 ha depending on the habitat, and can 52 therefore be more reliably used to infer population effects of a predator. However, they 53 provide a much less precise measure of predator activity, effectively devolving to presence 54 or absence in any given year. 55 Newson et al. (2010) addressed this problem by using smoothed relative abundance 56 surfaces to produce year-specific predator indices for each CBC site within their focal area 57 (England), effectively using broad-scale spatio-temporal trends to estimate variation in local 58 abundance. However, this approach may fail to capture variation in predator activity at the 59 narrower scale represented by the area of a typical CBC census plot, accurate 60 representation of which requires modelling at the individual site level. Here, therefore, I 61 reprise the approach used by Newson et al. (2010) for a wider range of potential prey 62 species, using indices of Sparrowhawk activity derived from site-level modelling. 63 Materials and Methods 64 Model structure 65 The approach used retains the basic structure of the model used by Newson et al. (2010) 66 (see appendix), and implements a regression of change in log prey population against 67 change in a log predator index: 푡−1 µ푖,푡 푃푖,푡 + 1 68 ln ( ) = ∑ 푟푗 + 훼. ln ( ) Equation 1 µ푖,1 푃푖,1 + 1 푗=1 bioRxiv preprint doi: https://doi.org/10.1101/491522; this version posted July 25, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 5 69 where µi,t is estimated prey population and Pi,t an estimate of predator activity in site i and 70 year t, rj is the instantaneous rate of change in global prey population caused by all factors 71 other than predator activity in year j, and α is the effect of the change in the log predator 72 index (ln(Pi,t + 1)) between the first year with site data (t=1) and year t. Change in the log 73 predator index underestimates change in log predator activity due to the need to 74 accommodate instances of zero activity by adding one, but remains highly correlated with it. 75 The model was implemented in R version 3.1.2 (R core team 2014) with prey population as 76 the response variable, using Poisson errors and a loge link: 77 푡−1 푃푖,푡 + 1 78 µ푖,푡 = exp [∑ 푟푗 + 훼. ln ( ) + ln µ푖,1] Equation 2 푃푖,1 + 1 푗=1 79 80 Estimates of rj emerge as year effects with each data year represented in the linear model as 81 a binary variable with the value 1 corresponding to all higher values of t at site level (i.e. the 82 effect of previous years is ‘present’) and otherwise as 0, while ln µi,1 is estimated as a site 83 effect, with each site represented as a level within a categorical variable (cf. Freeman & 84 Newson 2008), or in some cases as more than one level to take account of changes in the 85 size of the area censused. Variance in change in prey population between the first and any 86 subsequent year with site data is therefore partitioned between the effect of change in 87 predator activity over the same period, and the effect of conditions in each of the 88 intervening years. The implementation of Newson et al. (2010) included a number of 89 additional covariates, which are excluded here for reasons set out in the appendix. bioRxiv preprint doi: https://doi.org/10.1101/491522; this version posted July 25, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 6 90 Derivation of predator indices 91 CBC data were supplied by volunteer surveyors as part of a national scheme covering 92 around 250 plots each year. There was relatively high turnover and a policy of replacing a 93 lapsed plot with another of similar character, so the number of years surveyed at individual 94 sites varied considerably.
Load more

Recommended publications
  • Review of the Conflict Between Migratory Birds and Electricity Power Grids in the African-Eurasian Region
    CMS CONVENTION ON Distribution: General MIGRATORY UNEP/CMS/Inf.10.38/ Rev.1 SPECIES 11 November 2011 Original: English TENTH MEETING OF THE CONFERENCE OF THE PARTIES Bergen, 20-25 November 2011 Agenda Item 19 REVIEW OF THE CONFLICT BETWEEN MIGRATORY BIRDS AND ELECTRICITY POWER GRIDS IN THE AFRICAN-EURASIAN REGION (Prepared by Bureau Waardenburg for AEWA and CMS) Pursuant to the recommendation of the 37 th Meeting of the Standing Committee, the AEWA and CMS Secretariats commissioned Bureau Waardenburg to undertake a review of the conflict between migratory birds and electricity power grids in the African-Eurasian region, as well as of available mitigation measures and their effectiveness. Their report is presented in this information document and an executive summary is also provided as document UNEP/CMS/Conf.10.29. A Resolution on power lines and migratory birds is also tabled for COP as UNEP/CMS/Resolution10.11. For reasons of economy, documents are printed in a limited number, and will not be distributed at the meeting. Delegates are kindly requested to bring their copy to the meeting and not to request additional copies. The Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) and the Convention on the Conservation of Migratory Species of Wild Animals (CMS) REVIEW OF THE CONFLICT BETWEEN MIGRATORY BIRDS AND ELECTRICITY POWER GRIDS IN THE AFRICAN-EURASIAN REGION Funded by AEWA’s cooperation-partner, RWE RR NSG, which has developed the method for fitting bird protection markings to overhead lines by helicopter. Produced by Bureau Waardenburg Boere Conservation Consultancy STRIX Ambiente e Inovação Endangered Wildlife Trust – Wildlife & Energy Program Compiled by: Hein Prinsen 1, Gerard Boere 2, Nadine Píres 3 & Jon Smallie 4.
    [Show full text]
  • (2007): Birds of the Aleutian Islands, Alaska Please
    Bold* = Breeding Sp Su Fa Wi Bold* = Breeding Sp Su Fa Wi OSPREYS FINCHES Osprey Ca Ca Ac Brambling I Ca Ca EAGLES and HAWKS Hawfinch I Ca Northern Harrier I I I Common Rosefinch Ca Eurasian Sparrowhawk Ac (Ac) Pine Grosbeak Ca Bald Eagle* C C C C Asian Rosy-Finch Ac Rough-legged Hawk Ac Ca Ca Gray-crowned Rosy-Finch* C C C C OWLS (griseonucha) Snowy Owl I Ca I I Gray-crowned Rosy-Finch (littoralis) Ac Short-eared Owl* R R R U Oriental Greenfinch Ca FALCONS Common Redpoll I Ca I I Eurasian Kestrel Ac Ac Hoary Redpoll Ca Ac Ca Ca Merlin Ca I Red Crossbill Ac Gyrfalcon* R R R R White-winged Crossbill Ac Peregrine Falcon* (pealei) U U C U Pine Siskin I Ac I SHRIKES LONGSPURS and SNOW BUNTINGS Northern Shrike Ca Ca Ca Lapland Longspur* Ac-C C C-Ac Ac CROWS and JAYS Snow Bunting* C C C C Common Raven* C C C C McKay's Bunting Ca Ac LARKS EMBERIZIDS Sky Lark Ca Ac Rustic Bunting Ca Ca SWALLOWS American Tree Sparrow Ac Tree Swallow Ca Ca Ac Savannah Sparrow Ca Ca Ca Bank Swallow Ac Ca Ca Song Sparrow* C C C C Cliff Swallow Ca Golden-crowned Sparrow Ac Ac Barn Swallow Ca Dark-eyed Junco Ac WRENS BLACKBIRDS Pacific Wren* C C C U Rusty Blackbird Ac LEAF WARBLERS WOOD-WARBLERS Bold* = Breeding Sp Su Fa Wi Wood Warbler Ac Yellow Warbler Ac Dusky Warbler Ac Blackpoll Warbler Ac DUCKS, GEESE and SWANS Kamchatka Leaf Warbler Ac Yellow-rumped Warbler Ac Emperor Goose C-I Ca I-C C OLD WORLD FLYCATCHERS "HYPOTHETICAL" species needing more documentation Snow Goose Ac Ac Gray-streaked Flycatcher Ca American Golden-plover (Ac) Greater White-fronted Goose I
    [Show full text]
  • University of Cape Town
    Exploring the breeding diet of the Black Sparrowhawk (Accipiter Melanoleucus) on the Cape Peninsula Honours research project by Bruce Baigrie Biological Sciences Department: University of Cape Town Supervised by Dr. Arjun Amar Town Cape of University Page 1 of 33 The copyright of this thesis vests in the author. No quotation from it or information derived from it is to be published without full acknowledgementTown of the source. The thesis is to be used for private study or non- commercial research purposes only. Cape Published by the University ofof Cape Town (UCT) in terms of the non-exclusive license granted to UCT by the author. University Abstract This study investigates the diet of breeding Black Sparrowhawks (Accipiter melanoleucus) on the Cape Peninsula of South Africa. Macro-remains of prey were collected from below and around the vicinity of nests throughout the breeding seasons of 2012 and 2013. These prey items were then identified down to species where possible through the use of a museum reference collection. In both years 85.9% of the individual remains were those of Columbidae, which corresponds with the only other diet study on Black Sparrowhawks. Red- eyed Doves were the most common prey species, accounting for around 35% of the diet’s biomass and 45% of the prey items. Helmeted Guineafowl were also an important component of the diet for certain nests, making up on average 26.4% biomass of the diet. I found very little difference in diet between the different stages of breeding (pre-lay, incubation and nestling), despite the fact that females only contribute significantly during the nestling state and are considerably larger than the males.
    [Show full text]
  • Trip Report June 21 – July 2, 2017 | Written by Guide Gerard Gorman
    Austria & Hungary: Trip Report June 21 – July 2, 2017 | Written by guide Gerard Gorman With Guide Gerard Gorman and Participants: Jane, Susan, and Cynthia and David This was the first Naturalist Journeys tour to combine Austria and Hungary, and it was a great success. We visited and birded some wonderfully diverse habitats and landscapes in 12 days — the forested foothills of the Alps in Lower Austria, the higher Alpine peak of Hochkar, the reed beds around Lake Neusiedler, the grasslands and wetlands of the Seewinkel in Austria and the Hanság in Hungary, the lowland steppes and farmlands of the Kiskunság east of the Danube, and finally the pleasant rolling limestone hills of the Bükk in north-east Hungary. In this way, we encountered diverse and distinct habitats and therefore birds, other wildlife, and flora, everywhere we went. We also stayed in a variety of different family-run guesthouses and lodges and sampled only local cuisine. As we went, we also found time to take in some of the rich history and culture of these two countries. Wed., June 21, 2017 We met up at Vienna International Airport at noon and were quickly on our way eastwards into Lower Austria. It was a pleasant sunny day and the traffic around the city was a little heavy, but we were soon away from the ring-road and in rural Austria. Roadside birds included both Carrion and Hooded Crows, several Eurasian Kestrels, and Barn Swallows zoomed overhead. Near Hainfeld we drove up a farm road, stopped for a picnic, and did our first real birding.
    [Show full text]
  • Nature Quiz British Birds Birds of Prey
    Nature Quiz British Birds ­ Birds of Prey Birds of prey are birds that hunt for food primarily on the wing, using their keen senses, especially vision. Because of their predatory lifestyle, often at the top of the food chain, they face distinct conservation concerns. See how much you know in the following Natural History quiz on the subject. __________________________________________________________________________________ 1. What is the name of this bird? [ ] Golden Eagle [ ] Montagu's Harrier [ ] Common Buzzard [ ] White­tailed Eagle • Group: Buzzards, Kites and allies • Binomial: Circus pygargus • Order: Falconiformes • Family: Accipitridae • Status: Breeding Summer Visitor And Passage Migrant • It is an extremely rare breeding bird in the UK, and its status is precarious. • Each pair needs special protection. • It is a summer visitor, and migrates to Africa to spend the winter. A Resource From educationquizzes.com – The Number 1 Revision Site 2. What is the name of this bird? [ ] Common Buzzard [ ] Northern Goshawk [ ] European Honey­buzzard [ ] White­tailed Eagle • Group: Buzzards, Kites and allies • Binomial: Haliaeetus albicilla • Order: Falconiformes • Family: Accipitridae • Status: Resident Breeder And Widespread Introductions • It is the largest UK bird of prey. • It went extinct in the UK during the early 19th century, due to illegal killing, and the present population has been reintroduced. 3. What is the name of this bird? [ ] Common Buzzard [ ] Golden Eagle [ ] Northern Goshawk [ ] European Honey­buzzard • Group: Buzzards, Kites and allies • Binomial: Buteo buteo • Order: Falconiformes • Family: Accipitridae • Status: Resident Breeder And Passage Migrant • Pairs mate for life. • The male performs a ritual aerial display before the beginning of spring. • This spectacular display is known as 'the roller coaster'.
    [Show full text]
  • Prey Preferences and Recent Changes in Diet of a Breeding Population of the Northern Goshawk Accipiter Gentilis in Southwestern Europe
    Bird Study ISSN: 0006-3657 (Print) 1944-6705 (Online) Journal homepage: http://www.tandfonline.com/loi/tbis20 Prey preferences and recent changes in diet of a breeding population of the Northern Goshawk Accipiter gentilis in Southwestern Europe Salvador Rebollo, Gonzalo García-Salgado, Lorenzo Pérez-Camacho, Sara Martínez-Hesterkamp, Alberto Navarro & José-Manuel Fernández-Pereira To cite this article: Salvador Rebollo, Gonzalo García-Salgado, Lorenzo Pérez-Camacho, Sara Martínez-Hesterkamp, Alberto Navarro & José-Manuel Fernández-Pereira (2017): Prey preferences and recent changes in diet of a breeding population of the Northern Goshawk Accipiter gentilis in Southwestern Europe, Bird Study, DOI: 10.1080/00063657.2017.1395807 To link to this article: https://doi.org/10.1080/00063657.2017.1395807 View supplementary material Published online: 20 Nov 2017. Submit your article to this journal Article views: 19 View related articles View Crossmark data Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=tbis20 Download by: [178.57.158.158] Date: 23 November 2017, At: 04:33 BIRD STUDY, 2017 https://doi.org/10.1080/00063657.2017.1395807 Prey preferences and recent changes in diet of a breeding population of the Northern Goshawk Accipiter gentilis in Southwestern Europe Salvador Rebollo a, Gonzalo García-Salgadoa, Lorenzo Pérez-Camachoa, Sara Martínez-Hesterkampa, Alberto Navarrob and José-Manuel Fernández-Pereirac aEcology and Forest Restoration Group, Department of Life Sciences, University of Alcalá, Madrid, Spain; bAsturias, Spain; cPontevedra, Spain ABSTRACT ARTICLE HISTORY Capsule: Northern Goshawk Accipiter gentilis diet has changed significantly since the 1980s, Received 2 December 2016 probably due to changes in populations of preferred prey species.
    [Show full text]
  • Analysis of Partial Migration Strategies of Central European Raptors Based on Ring Re-Encounter Data
    Analysis of partial migration strategies of Central European raptors based on ring re-encounter data I n a u g u r a l d i s s e r t a t i o n zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften (Dr. rer. nat.) der Mathematisch-Naturwissenschaftlichen Fakultät der Ernst-Moritz-Arndt-Universität Greifswald vorgelegt von Daniel Holte geboren am 06.10.1981 in Neuss Greifswald, den 14.06.201828.03.2018 Dekan: Prof. Dr. Werner Weitschies 1. Gutachter : PD Dr. Martin Haase 2. Gutachter: Dr. Sven Renner Tag der Promotion: 14.06.2018 Table of Contents A. Synopsis 7 1. General introduction 7 1.1 Marking animals 7 1.1.1 Bird ringing 8 1.2 Bird migration 10 1.2.1 Partial migration 11 1.3 Target species 11 1.3.1 Common kestrel 12 1.3.2 Common buzzard 12 1.3.3 Eurasian sparrowhawk 13 1.4 Study aims and hypotheses 13 2. Methods 15 2.1 Partial migration 15 2.2 Predicting ring re-encounters considering spatial observer heterogeneity 16 3. Results and Discussion 18 3.1 Partial migration 18 3.2 Predicting ring re-encounters considering spatial observer heterogeneity 21 4. Cited literature 25 B. Manuscripts 29 Paper I 29 Paper II 47 Paper III 65 Contributions to manuscripts 95 C. Eigenständigkeitserklärung 97 D. Curriculum Vitae 99 E. Scientific contributions 101 F. Danksagung 103 A. Synopsis 1. General introduction The history of ornithology goes far back in human history and its beginning is probably not clearly definable. Already in the fourth century B.C., Aristotle described about 140 bird species and he declared the study of birds to be a worthy activity for philosophers, which made ornithology become a science (Stresemann 1951).
    [Show full text]
  • Scotland in Style
    SCOTLAND IN STYLE MAY 1-10, 2020 ©2019 Please note this tour may be taken in connection with Wild & Ancient Britain with Ireland cruise , May 11-26, 2020. Cairngorms National Park © Andrew Whittaker This short, one hotel tour provides an enormously varied and comprehensive taste of all that the bonnie Scottish Highlands have to offer. During our seven full days based around Strathspey and the spectacular Cairngorms National Park, there will be a varied and flexible daily program of events. Although the main focus is on birding excursions, we will be centrally located to visit many fine castles, battlefields, and sites of historical significance, plus we’ll enjoy a guided visit to a famous Scotch single malt whisky distillery. Scotland in Style, Page 2 The Highlands scenery is the most dramatic in the British Isles: the highest peaks in Britain; extensive remote moorlands; large tracts of ancient woodland of Caledonian Pines; stunning coastal scenery of cliffs, inlets, lochs, and offshore islands; and vast tracts of prehistoric peat bog and fast-flowing, crystal clear rivers. We will target localized and rare specialties such as Eurasian Capercaillie (rare), Black Grouse, Rock Ptarmigan, Willow Ptarmigan (the British subspecies known as Red Grouse, an excellent candidate for a future split and another endemic), the gorgeous Mandarin Duck, the endemic Scottish Crossbill, localized Ring Ouzel, Crested Tit, Horned Grebe, Arctic and Red-throated loon, and raptors such as the striking Red Kite, Eurasian Sparrowhawk, Eurasian Buzzard, and Golden and White-tailed eagle (rare). Most of these breed only within the British Isles, exclusively here in this wild region of Scotland, and we have good chances of seeing most of them.
    [Show full text]
  • Population Trends of Common European Breeding Birds 2011
    document. be made of the information contained in this this in contained information the of made be may that use any for responsible not is Commission is report lies with the authors; the European European the authors; the with lies report is th of contents the for responsibility Sole RSPB. and and since January 2006 by the European Commission Commission European the by 2006 January since and UK), the in Partner International BirdLife the Sweden United Kingdom United Switzerland nancially since 2002 by the Royal Society for Protection of Birds (RSPB, (RSPB, Birds of Protection for Society Royal the by 2002 since nancially fi supported been has It Pan-European Common Bird Monitoring Scheme (PECBMS) Scheme Monitoring Bird Common Pan-European Census Council (EBCC) and BirdLife International. International. BirdLife and (EBCC) Council Census Bird European the of initiative joint a is PECBMS A. R. Renwick. Renwick. R. A. Breeding Birds 2011. CSO, Prague. CSO, 2011. Birds Breeding M. Anton, S. Herrando, Å. Lindström, H. Schmid, K. Risely, D. G. Noble, Noble, G. D. Risely, K. Schmid, H. Lindström, Å. Herrando, S. Anton, M. Slovenia Spain Citation: Citation: PECBMS 2011. Population Trends of Common European European Common of Trends Population 2011. PECBMS K. Slabeyová, J. Ridzoň, J. Topercer, V. Escandell, J. C. del Moral, Moral, del C. J. Escandell, V. Topercer, J. Ridzoň, J. Slabeyová, K. wicz, P. Chylarecki, D. Leitão, R. Martins, A. Meirinho, J. Figelj, P. Kmecl, Kmecl, P. Figelj, J. Meirinho, A. Martins, R. Leitão, D. Chylarecki, P. wicz, Cover photo: Cover Common Coots by Z. Tunka (birdphoto.cz).
    [Show full text]
  • Aspects of Breeding Ecology of the Brown Goshawk (Accipiter Fasciatus) in an Urban Environment in Northern Australia
    Northern Territory Naturalist (2015) 26: 32–43 Research Article Aspects of breeding ecology of the Brown Goshawk (Accipiter fasciatus) in an urban environment in northern Australia William E. Riddell 20/17 Geranium Street, The Gardens, NT 0820, Australia. Email: [email protected] Abstract The breeding parameters of the Brown Goshawk (Accipiter fasciatus) have yet to be documented in an urban environment in Australia. Twenty-six active nests were located in urban Darwin during the 2013–2014 breeding season. Incubation occurred from August to November over a 12 week laying period. Twenty-two nests were in introduced African Mahogany trees (Khaya senegalensis) and four were in River Red Gums (Eucalyptus camaldulensis). One or more young matured to fledgling stage or later at 17 of the 26 nests, with an average fledging rate of 1.13 young per nest. Assuming that all active nests were detected, the breeding density of Brown Goshawks across the study area is 52 nests per 100 km2, which is higher than that recorded in previous studies on the species. Introduction The Brown Goshawk (Accipiter fasciatus) occurs throughout mainland Australia and on the surrounding islands, including Wallacea, New Guinea, New Caledonia and the Solomon Islands (Debus 2012). The species occurs in wooded and forested lands of tropical and temperate Australia. Abundance is highest in woodland or open forest but a variety of habitats are used, with individuals occurring wherever trees or tall shrubs provide cover for ambushing prey (Marchant & Higgins 1993). Incubation lasts 29–31 days with fledging occurring at 28–37 days (Olsen et al. 1982). The breeding parameters of the Brown Goshawk have previously been described in southern Victoria (Aumann 1989) and north-eastern Queensland (Burton et al.
    [Show full text]
  • The Eurasian Sparrowhawk
    The Eurasian Sparrowhawk Background Sparrowhawks ( Accipiter nisus ) are small birds of prey belonging to the hawk family, with about six sub-species, the nominate occurring across UK, Iberia, and Fennoscandia and east to Siberia. It is predominantly a lowland bird of prey, largely frequenting wooded areas, where it hunts for small birds. Where are they found and how many are there? Sparrowhawks are widespread in Britain and Ireland, though they are often absent or at very low densities in upland areas of Scotland, as well as the Western Isles and Shetland. Its absence here may be largely due to absence of suitable breeding habitat rather than absence of prey. It is even found in many towns and cities, with Edinburgh alone supporting about 30-40 breeding pairs. Densities are highest in lowland & southern Scotland, and lowest in the north-west and some island groups. The British population is about 32,000 breeding pairs with some 8,000-12,000 pairs in Scotland. Sparrowhawks breed in both conifer and broadleaved woods, but may hunt over open farmland, coastal habitats and in built-up areas. Sparrowhawks in Britain are largely sedentary, though the British population is joined in winter by birds from north-western Europe and Scandinavia. Where and when do they breed? Sparrowhawks breed in wooded areas, typically conifer plantations that are not too dense or too open, as well as broadleaved woodland. Conifer plantations about 20- 40 years old are particularly suitable. Breeding sites are changed often despite the birds being sedentary. Nest building occurs in April and about 3 – 6 eggs are usually laid in May.
    [Show full text]
  • Specialized Photoreceptor Composition in the Raptor Fovea
    Received: 19 October 2016 | Revised: 13 January 2017 | Accepted: 7 February 2017 DOI 10.1002/cne.24190 The Journal of RESEARCH ARTICLE Comparative Neurology Specialized photoreceptor composition in the raptor fovea Mindaugas Mitkus1 | Peter Olsson1 | Matthew B. Toomey2 | Joseph C. Corbo2 | Almut Kelber1 1Lund Vision Group, Department of Biology, Lund University, Lund, Sweden Abstract 2Department of Pathology and Immunology, The retinae of many bird species contain a depression with high photoreceptor density known as Washington University School of Medicine, the fovea. Many species of raptors have two foveae, a deep central fovea and a shallower tempo- St. Louis, Missouri ral fovea. Birds have six types of photoreceptors: rods, active in dim light, double cones that are Correspondence thought to mediate achromatic discrimination, and four types of single cones mediating color Mindaugas Mitkus, Lund Vision Group, vision. To maximize visual acuity, the fovea should only contain photoreceptors contributing to Department of Biology, Lund University, Solvegatan€ 35, Lund 22362, Sweden. high-resolution vision. Interestingly, it has been suggested that raptors might lack double cones in Email: [email protected] the fovea. We used transmission electron microscopy and immunohistochemistry to evaluate this Funding information claim in five raptor species: the common buzzard (Buteo buteo), the honey buzzard (Pernis apivorus), MM, PO, and AK were funded by the the Eurasian sparrowhawk (Accipiter nisus), the red kite (Milvus milvus), and the peregrine falcon Swedish Research Council (VR2012-2212), (Falco peregrinus). We found that all species, except the Eurasian sparrowhawk, lack double cones the Human Frontier Science Program grant #RGP0017/2011 and the K & A in the center of the central fovea.
    [Show full text]