DOCSLIB.ORG

Red Crossbill Types, Settle Most Readily in Areas Where Cone Sizes and Types Are Most Similar to Those Found in Core Range

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Red Crossbill Types, Settle Most Readily in Areas Where Cone Sizes and Types Are Most Similar to Those Found in Core Range SSttaattuuss aanndd ddiissttrriibbuuttiioonn ooff TTyyppee 11 RReedd CCrroossssbbiillll ((LLooxxiiaa ccuurrvviirroossttrraa )):: aann AAppppaallaacchhiiaann CCaallll TTyyppee?? MATTHEW A. YOUNG • CORNELL LAB OF ORNITHOLOGY • 159 SAPSUCKER WOODS ROAD, ITHACA, NEW YORK 14850 • OMAY6NCORNELL.EDUP KEN BLANKENSHIP • 2400 BARRETT CREEK BOULEVARD #827, MARIETTA, GEORGIA 30066 • OKENHBLANKENSHIPNCOMCAST.NETP MARILYN WESTPHAL • P. O. BOX 1427, HENDERSONVILLE, NORTH CAROLINA 28793 • OMJWESTPHNRET.UNCA.EDUP STEVE HOLZMAN • 349 JEFFERSON ROAD, BISHOP, GEORGIA 30621 • OSTEVE_HOLZMANNYAHOO.COMP records of our own, and also adduce the broad - er natural history of this Type, using primarily recent records of calling birds that have been identified by audiospectrographic analysis. We review evidence that Type 1 is not a specialist on a single species of conifer (as some Types appear to be), and from that we infer that wan - derings away from the core breeding range in Appalachia are driven by cone crop failures of several species. We further suggest that wan - dering Type 1 birds, which have medium-sized bills among the Red Crossbill Types, settle most readily in areas where cone sizes and types are most similar to those found in core range. We urge observers to audio-record Red Crossbills wherever they are detected and to note the species of conifer in which they are observed, to increase our understanding of their complex natural histories. Background: Red Crossbill Types and their natural histories Red Crossbill ( Loxia curvirostra ) has been di - vided into ten “call types” (hereafter Types 1- 10) in North America; in addition to differ - ences in flight calls, small but significant dif - ferences in bill morphology, ecology, and ge - netics distinguish these Types (Groth 1993c, Benkman 1999, Parchman et al. 2006, Irwin 2010). Groth (1993c) was the first to assert that the Types meet criteria for full-species sta - tus under both phylogenetic and biological species concepts and that they should there - fore be recognized as taxonomic species. More recent studies continue to inform discussion of Red Crossbill’s taxonomic status. Sewall (2009, 2011) and Sewall and Hahn (2009) present ev - idence to support the ideas that Red Crossbill This Red Crossbill was audio-recorded and confirmed as Type 1, a Type that appears to be predominantly an Appalachian bird. flight calls are an example of reliable signaling This individual was photographed along Persimmon Road, Clayton, Georgia on 5 July 2008. Photograph by Darlene Moore. and that adults show limited learning of vocal - izations. Benkman (2007) and Benkman et al. Abstract Northwest have at times called this association (2009) argue that Types are effectively repro - Red Crossbill ( Loxia curvirostra ) of Type 1 has into question. In this paper, we review evi - ductively isolated. Interbreeding between been considered chiefly an Appalachian bird, dence in support of this association (n=186 Types seems to be relatively rare, despite sym - though detections of this Type as far away from Appalachian recordings of Type 1, n=14 non- patry of several Types and widespread wander - Appalachia as New England and the Pacific Appalachian recordings of Type 1), including ing by many Types. In several published stud - 554 NORTH AMERICAN BIRDS STATUS AND DISTRIBUTION OF TYPE 1 RED CROSSBILL: AN APPALACHIAN CALL TYPE? ies, interbreeding between various Types has been estimated at up to 5% (Groth 1993b, Summers et al. 2007, Benkman et al. 2009). In the South Hills of Idaho, where the resident population (Type 9) occurs sympatrically with Types 2 and 5, interbreeding was found to be less than 1% among 1704 paired crossbills (Benkman et al. 2009). Similarly, in a Euro - pean study of sympatrically occurring Red (or Common) Crossbills ( L. curvirostra ), Parrot Crossbills ( L. pytyopsittacus ), and Scottish Crossbills ( L. scotica ), Summers et al. (2007) Figure 1. A male Type 1 Red Crossbill with a fledgling visible in the left part of the frame (at left); the same male is shown found evidence of hybridization in approxi - feeding a different fledgling (right). These birds were audio-recorded and photographed in Rabun County, Georgia on 25 mately 5% of pairs, mostly between the larger- April 2009. Images from video by Ken Blankenship. billed Parrot Crossbill and Scottish Crossbill. Benkman (1993a) further predicted the exis - conclusively documented for a few; definitive In a study of sympatrically occurring Types 1 tence of a Sitka Spruce ( P. sitchensis )-associated evidence of specialization for a primary and 2 in the mountains of Virginia and North Type—and indeed Irwin recently (2010) de - conifer is lacking for Types 1, 6, and 7. Carolina in the 1980s, Groth (1993b) found scribed Type 10 in the coastal Sitka Spruce Benkman (2007) suggested that Type 1 might that all 60 monitored birds paired with mem - forests of northern California. specialize on Red Spruce ( P. rubens ), a species bers of their own Types. The evolution of dietary specialization in largely confined to the Northeast (defined Types differ in bill depth and palate groove crossbill Types is readily understandable in here as the area from the Adirondack Moun - structures, and Benkman (1993a) proposed insular populations such as those of New - tains northward and northeastward to the that each Type is most efficient at feeding on foundland Red Crossbill (Benkman 1989, Canadian Maritimes). However, Red Spruce single key species of conifer, although not Benkman 1993b, Benkman and Parchman is also found in small isolated pockets along obligatorily. Other authors have proposed that 2009) or Hispaniolan Crossbill ( L. megapla - the spine of the central and southern Ap - certain Types have core zones of occurrence ga ) (Benkman 1994); it is also clear how is - palachians from Pennsylvania to North Car - where they regularly breed and are most com - land-like geography, such as Idaho’s South olina, and Groth originally thought that mon (Dickerman 1987, Knox 1992, Kelsey Hills, could give rise to differentiated cross - medium-billed Type 1 might be primarily an 2008, Young 2010a). While most Types do ap - bill populations, particularly where relatively Appalachian bird, but he later recorded two pear to forage most efficiently on a single stable cone crops are found (Benkman et al. Type 1 birds in British Columbia and set species of conifer when in their core zone of oc - 2009). Such specialization in other Types is aside the concept of an Appalachian Red currence (Benkman 1993a), they also feed on less clearly motivated and indeed is not yet Crossbill (Groth 1993c). seeds of multiple coniferous species and can be seen switching to those conifers that provide Table 1 . Estimated conifer seed usage through the cone cycle year (June through May) for Type 1 Red Crossbill, as well the highest energy yields throughout the cone as usage of insects and bird feeding stations. These estimates are based on our field observations, as well as on our un - derstanding of cone-ripening phenologies and Type 1’s bill morphology. Southeast (SE) and Northeast (NE) are abbrevi - cycle (Benkman 1987, 1988). In North Ameri - ated herein. ca, Benkman (1993a) indicates that Type 2 ap - pears to be most efficient at feeding on Pon - Conifer/Area Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May derosa Pine ( Pinus ponderosa scopularum ), Type White Spruce (NE) X X X X X-x X-x X-x x-o x-o x-o 3 on Western Hemlock ( Tsuga heterophylla ), Red Spruce (NE and SE) X X X X X-x X-x x-x x-o x-o x-o x-o Type 4 on Douglas-fir ( Pseudotsuga menziesii European Larch (Southern New York) x x x x x x x x x x x x menziesii ), and Type 5 on Lodgepole Pine ( Pi - White Pine (East) x X X X X-x X-x x-o x-o nus contorta ). Benkman (1993b) suggests that Type 8 feeds most efficiently on Black Spruce Eastern Hemlock (East) x x x x x x x x x x x (Picea mariana ). And Benk - Red Pine (NE) x-X X X X man et al. (2009) note that Virginia Pine (mostly SE) x-X X X X Type 9—which has already Pitch Pine (mostly SE) x-X X X X been proposed as a full Shortleaf Pine (SE) x-X X X X species, South Hills Crossbill (L. sinesciurus )—feeds most Loblolly Pine (Georgia) x-X X X X efficiently on an isolated pop - Norway Spruce (Southern New York) x x x x-X X X X X ulation of Lodgepole Pine. Insects x x Feeders o-x o-x o-x o-x x x Figure 2. Audiospectrograph of Type 1 Red Crossbill, considered diagnostic, KEY: recorded 19 June 1983 in Montgomery X = used often County, Virginia by Jeffrey Groth. The x = used less frequently dark horizontal marks on the right sides X-x = birds are using resource less and starting to transition to other conifers of image are for kHz lines 3, 5, and 7. x-X = birds are transitioning from other conifers to a new conifer Image used and adapted from Groth o-x = birds could start utilizing alternative resource (e.g., feeders), depending on availability of others (1993a) with permission of the author. x-o = birds have exhausted resource VOLUME 65 (2011) • NUMBER 3 555 STATUS AND DISTRIBUTION OF TYPE 1 RED CROSSBILL: AN APPALACHIAN CALL TYPE? Table 2 . Totals of Red Crossbills from Red Spruce areas of the Appalachians in North Carolina during mid- through late May surveys conducted by Mar - ilyn Westphal. Note the absence of Red Crossbills on most May surveys. Date / Location Black Mountains Balsam Mountains Buncombe May 2006 18 0 0 May 2007 0 0 0 May 2008 0 (no survey) 0 May 2009 0 0 0 May 2010 1 0 0 May 2011 32 2 0 History of Type 1 in the Appalachian Mountains McNair (1988) provides a thorough review of historical Red Crossbill breeding records from the southern Appalachians, from the Virginias to Georgia.
Load more

Recommended publications
  • Red Crossbill Loxia Curvirostra Many Members of the Finch Family Migrate Irregu- Larly, As Demanded by the Irregularity of Their Food Supply
    584 Finches — Family Fringillidae Red Crossbill Loxia curvirostra Many members of the finch family migrate irregu- larly, as demanded by the irregularity of their food supply. The crossbills, with their unique specializa- tion and dependence on conifer seeds, take this irregularity to an extreme. With only small areas for- ested in conifers, San Diego County cannot support a population of the Red Crossbill, so the species is a sporadic visitor here, though it has attempted nest- ing in the county at least once. Studies of morphol- ogy, genetics, and voice suggest the Red Crossbill, with its great variation across North America in size and bill shape, may consist of multiple cryptic Photo by Anthony Mercieca species. Winter: The winters of 1966–67, 1984–85, and 1996–97 saw the biggest incursions of the Red Crossbill known the Laguna Mountains in late July 1993 (G. L. Rogers, P. in the history of San Diego County. Thus the 5-year atlas A. Ginsburg, AB 47:1152, 1993). From 1997 to 2001 the period 1997–2002 began with the winding down of an only such reports were from Middle and Cuyamaca peaks incursion in which small flocks were seen through much (M20), with one on 19 May 1998 and one or two 23–24 of the county, such as 10 at the Vineyard Golf Course, June 2001 (S. Peterson, D. Holway). Escondido (K11), 17 February 1997 (E. C. Hall). The Conservation: The crossbills breeding in the southwest- Oceanside Christmas bird count yielded the maximum of ern quadrant of the contiguous United States have bills 24 on 29 December 1996, and up to 10 occurred even at adapted to feed on the seeds of pines.
    [Show full text]
  • Condition of Designated Sites
    Scottish Natural Heritage Condition of Designated Sites Contents Chapter Page Summary ii Condition of Designated Sites (Progress to March 2010) Site Condition Monitoring 1 Purpose of SCM 1 Sites covered by SCM 1 How is SCM implemented? 2 Assessment of condition 2 Activities and management measures in place 3 Summary results of the first cycle of SCM 3 Action taken following a finding of unfavourable status in the assessment 3 Natural features in Unfavourable condition – Scottish Government Targets 4 The 2010 Condition Target Achievement 4 Amphibians and Reptiles 6 Birds 10 Freshwater Fauna 18 Invertebrates 24 Mammals 30 Non-vascular Plants 36 Vascular Plants 42 Marine Habitats 48 Coastal 54 Machair 60 Fen, Marsh and Swamp 66 Lowland Grassland 72 Lowland Heath 78 Lowland Raised Bog 82 Standing Waters 86 Rivers and Streams 92 Woodlands 96 Upland Bogs 102 Upland Fen, Marsh and Swamp 106 Upland Grassland 112 Upland Heathland 118 Upland Inland Rock 124 Montane Habitats 128 Earth Science 134 www.snh.gov.uk i Scottish Natural Heritage Summary Background Scotland has a rich and important diversity of biological and geological features. Many of these species populations, habitats or earth science features are nationally and/ or internationally important and there is a series of nature conservation designations at national (Sites of Special Scientific Interest (SSSI)), European (Special Area of Conservation (SAC) and Special Protection Area (SPA)) and international (Ramsar) levels which seek to protect the best examples. There are a total of 1881 designated sites in Scotland, although their boundaries sometimes overlap, which host a total of 5437 designated natural features.
    [Show full text]
  • A Hybrid Red Crossbill-Pine Siskin (Loxia Curvirostra X Carduelis Pinus
    January1984] ShortCommunications 155 HILLS, M. 1978. On ratios--a response to Atchley, nov, Cramer-Von Mises and related statistics Gaskins and Anderson. Syst. Zool. 27: 61-62. without extensive tables. J. Amer. Stat. Assoc. 69: SAS INSTITUTE.1982. SAS user's guide: basics.Cary, 730. North Carolina, SAS Institute, Inc. ZAR, J. H. 1974. Biostatisticalanalysis. Englewood SHAPIRO,S.S., & M. B. WILK. 1965. An analysis of Cliffs, New Jersey,Prentice-Hall, Inc. variance test for normality (complete samples). Biometrika 52:591-611. Received3 March 1983,accepted 6 September1983. STEPHENS,M.A. 1974. Use of the Kolmogorov-Smir- A Hybrid Red Crossbill-Pine Siskin (Loxia curvirostra x Carduelis pin us) and Speculations on the Evolution of Loxia DAN A. TALLMAN • AND RICHARD L. ZUSI 2 'Departmentof Mathematics,Natural Sciences and Health Professions, Northern State College, Aberdeen,South Dakota 57401 USA; and 2National Museum of NaturalHistory, SmithsonianInstitution, Washington, D.C. 20560 USA On the morning of 27 December1981, a strange streaksweakest on lower throat and belly and dark- finch appeared at Tallman's feeder in a residential est and best defined on flanks and crissum. backyardin Aberdeen,Brown County, South Dakota. Upperparts dusky olive streaked or spotted with Alone and in the companyof Pine Siskins,the bird dark gray. Feathersof forehead and crown dark with consumedsunflower seeds.It fed on the ground and whitish or yellowish edges, giving spotted effect. alsocracked seeds while perchedon a sunflowerhead Longer feathers of nape, neck, and back dark gray hung from a clothesline.Tallman noted that this finch, borderedwith dusky olive laterally, giving streaked when approached,did not fly with a small siskin effect.
    [Show full text]
  • Scotland 2014 Outer Hebrides & the Highlands
    Scotland 2014 Outer Hebrides & the Highlands 22 May – 7 June 2014 St Kilda Wren, Hirta, St Kilda, Scotland, 30 May 2014 (© Vincent van der Spek) Vincent van der Spek, July 2014 1 highlights Red Grouse (20), Ptarmigan (4-5), Black Grouse (5), American Wigeon (1), Long- tailed Duck (5), three divers in summer plumage: Great Northern (c. 25), Red- throated (dozens) and Black-throated (1), Slavonian Grebe (1), 10.000s of Gannets and 1000s of Fulmars, Red Kite (5), Osprey (2 different nests), White-tailed Eagle (8), Golden Eagle (1), Merlin (2), Corncrake (2), the common Arctic waders in breeding habitat, Dotterel (1), Pectoral Sandpiper (1), sum plum Red-necked Phalarope (2), Great Skua (c. 125), Glaucous Gull (1), Puffin (c. 20.000), Short- eared Owl (1), Rock Dove (many), St Kilda Wren (8), other ssp. from the British Isles (incl. Wren Dunnock and Song Thrush from the Hebrides), Ring Ouzel (4), Scottish Crossbill (9), Snow Bunting (2), Risso’s Dolphin (4), Otter (1). missed species Capercaillie, ‘Irish’ Dipper ssp. hibernicus, the hoped for passage of Long-tailed and Pomarine Skuas, Midgets. Ptarmigan, male, Cairn Gorm, Highlands, Scotland, 3 June 2014 (© Vincent van der Spek) 2 introduction Keete suggested Scotland as a holiday destination several times in the past, so after I dragged her to many tropical destinations instead it was about time we went to the northern part of the British Isles. And I was not to be disappointed! Scotland really is a beautiful place, with great people. Both on the isles, with its wild and sometimes desolate vibe and very friendly folks and in the highlands, there seemed to be a stunning view behind every stunning view.
    [Show full text]
  • Phylogeography of Finches and Sparrows
    In: Animal Genetics ISBN: 978-1-60741-844-3 Editor: Leopold J. Rechi © 2009 Nova Science Publishers, Inc. Chapter 1 PHYLOGEOGRAPHY OF FINCHES AND SPARROWS Antonio Arnaiz-Villena*, Pablo Gomez-Prieto and Valentin Ruiz-del-Valle Department of Immunology, University Complutense, The Madrid Regional Blood Center, Madrid, Spain. ABSTRACT Fringillidae finches form a subfamily of songbirds (Passeriformes), which are presently distributed around the world. This subfamily includes canaries, goldfinches, greenfinches, rosefinches, and grosbeaks, among others. Molecular phylogenies obtained with mitochondrial DNA sequences show that these groups of finches are put together, but with some polytomies that have apparently evolved or radiated in parallel. The time of appearance on Earth of all studied groups is suggested to start after Middle Miocene Epoch, around 10 million years ago. Greenfinches (genus Carduelis) may have originated at Eurasian desert margins coming from Rhodopechys obsoleta (dessert finch) or an extinct pale plumage ancestor; it later acquired green plumage suitable for the greenfinch ecological niche, i.e.: woods. Multicolored Eurasian goldfinch (Carduelis carduelis) has a genetic extant ancestor, the green-feathered Carduelis citrinella (citril finch); this was thought to be a canary on phonotypical bases, but it is now included within goldfinches by our molecular genetics phylograms. Speciation events between citril finch and Eurasian goldfinch are related with the Mediterranean Messinian salinity crisis (5 million years ago). Linurgus olivaceus (oriole finch) is presently thriving in Equatorial Africa and was included in a separate genus (Linurgus) by itself on phenotypical bases. Our phylograms demonstrate that it is and old canary. Proposed genus Acanthis does not exist. Twite and linnet form a separate radiation from redpolls.
    [Show full text]
  • Britain's First Two-Barred Crossbill
    Britain’s first Two-barred Crossbill Andrew H. J. Harrop, Alan G. Knox and Robert Y. McGowan, on behalf of the British Ornithologists’ Union Records Committee Introduction isations that suggest that the three forms would Until 1998, the British Ornithologists’ Union be best treated as separate species (Benkman (BOU) compiled a single List of the birds of 1992; Elmberg 1993; Cramp & Perrins 1994; Britain & Ireland. Following a request from the AOU 1998). These differences are sufficiently Irish Rare Birds Committee, the BOU has since marked to be observable in the field. The His- then maintained a List for Britain alone (BOU paniolan Crossbill, now treated as a separate 1999). This has entailed ongoing work to sepa- species by the AOU (2003), is not discussed rate the two Lists and establish, among other here; for further information see Benkman things, the first acceptable records for Britain of (1994), Smith (1997) and Boon et al. (2006). those species and subspecies whose first British As a species, Loxia leucoptera was given its and Irish record came from Ireland. A number formal scientific name by Gmelin in 1789, of these were listed in recent BOURC reports in based on specimens of the American White- Ibis and by Bradshaw (2003). winged Crossbill brought to Europe from The first Two-barred Crossbill Loxia leu- Hudson Bay and New York. Therefore, early ref- coptera for Britain & Ireland was a female of the erences to this bird in Britain were generally Old World race L. l. bifasciata (hereafter under the name ‘White-winged Crossbill’ and referred to as bifasciata), shot at Grenville, near believed to relate to birds from America (e.g.
    [Show full text]
  • RSPB CENTRE for CONSERVATION SCIENCE RSPB CENTRE for CONSERVATION SCIENCE Where Science Comes to Life
    RSPB CENTRE FOR CONSERVATION SCIENCE RSPB CENTRE FOR CONSERVATION SCIENCE Where science comes to life Contents Knowing 2 Introducing the RSPB Centre for Conservation Science and an explanation of how and why the RSPB does science. A decade of science at the RSPB 9 A selection of ten case studies of great science from the RSPB over the last decade: 01 Species monitoring and the State of Nature 02 Farmland biodiversity and wildlife-friendly farming schemes 03 Conservation science in the uplands 04 Pinewood ecology and management 05 Predation and lowland breeding wading birds 06 Persecution of raptors 07 Seabird tracking 08 Saving the critically endangered sociable lapwing 09 Saving South Asia's vultures from extinction 10 RSPB science supports global site-based conservation Spotlight on our experts 51 Meet some of the team and find out what it is like to be a conservation scientist at the RSPB. Funding and partnerships 63 List of funders, partners and PhD students whom we have worked with over the last decade. Chris Gomersall (rspb-images.com) Conservation rooted in know ledge Introduction from Dr David W. Gibbons Welcome to the RSPB Centre for Conservation The Centre does not have a single, physical Head of RSPB Centre for Conservation Science Science. This new initiative, launched in location. Our scientists will continue to work from February 2014, will showcase, promote and a range of RSPB’s addresses, be that at our UK build the RSPB’s scientific programme, helping HQ in Sandy, at RSPB Scotland’s HQ in Edinburgh, us to discover solutions to 21st century or at a range of other addresses in the UK and conservation problems.
    [Show full text]
  • Engelsk Register
    Danske navne på alverdens FUGLE ENGELSK REGISTER 1 Bearbejdning af paginering og sortering af registret er foretaget ved hjælp af Microsoft Excel, hvor det har været nødvendigt at indlede sidehenvisningerne med et bogstav og eventuelt 0 for siderne 1 til 99. Tallet efter bindestregen giver artens rækkefølge på siden.
    [Show full text]
  • The Flight Calls of Crossbills Migrating Over a Southern Pennine Watch Point in Autumn 2019
    THE FLIGHT CALLS OF CROSSBILLS MIGRATING OVER A SOUTHERN PENNINE WATCH POINT IN AUTUMN 2019 D.H. Pennington, January 2020 INTRODUCTION In recent years, my birding interest has increasingly been focussed on autumn visible migration in the South Pennines. This has mostly taken place at Harden, on the border of South and West Yorkshire, in the company of Nick Mallinson and, until 2016, Mick Cunningham. In 2014, I began experimenting with sound recording at this site, and this, among several other benefits, soon had the effect of drawing attention to the variations in the flight calls of migrating Common Crossbills. At first, virtually all of these variations were shown by sonograms to belong to one or the other of just two ‘types’. However, this all changed in 2019, when despite it being a very poor autumn in terms of the number of birds passing over (see here for a yearly comparison), at least five different crossbill flight calls were detected. The aims of this article are to document these latest occurrences and, drawing on recently published research, put them into a wider context. CROSSBILL ‘TYPES’? Variability in the vocalisations of Common Crossbills has long been acknowledged, with their flight calls and excitement calls showing the most obvious diversification. However, several studies over the past three decades have shown that individuals are in fact very limited in their call repertoire, and that birds using any particular flight call will invariably use the same associated excitement call. Hence, each individual can be assigned to a vocal ‘type’ (see e.g. Groth 1993, Robb 2000).
    [Show full text]
  • On the Advantages of Crossed Mandibles: an Experimental Approach
    IBIS 130: 288-293 On the advantages of crossed mandibles: an experimental approach CRAIG W. BENKMAN* Department of Biological Sciences, State Uniwersity of New York at Albany, 1400 Washington Avenue, Albany, New York 12222, USA Accepted 20 November 1986 The importance of the crossed mandibles to crossbills for foraging on conifer cones was studied by removing most of the crossed portion of the mandibles of two Red Crossbills L. curuirortra. The foraging rate of these two bill-altered crossbills on the cones of three species of conifers was compared to their rates prior to bill alteration and to two controls. The mandible crossing proved essential for extracting seeds from closed cones. However, as cones open the bill crossing becomes less critical. The mandible crossing appears to be one of several adaptationsof crossbills that have extended the period during which conifer seeds can be exploited effectively. The functions of morphological structures can often be understood by detailed observations of organisms. However, a difficulty with ascribing a function to a structure by observation alone is that different observers often come to different conclusions. Experimental investigations of function are desirable but are often either difficult or trivial. For example, removing a bird’s leg would make perching or terrestrial locomotion impossible or awkward. In some cases, however, slight modification of structures may provide a means for studying a structure’s utility. One striking example of the difficulty of attributing a function to a structure by observation alone is the crossed mandibles of crossbills Loxia. There have been many opinions as to the function of the mandible crossing ranging from those suggesting no adaptive value to those suggesting a specific adaptive function.
    [Show full text]
  • Loxia Scotica
    Loxia scotica -- Hartert, 1904 ANIMALIA -- CHORDATA -- AVES -- PASSERIFORMES -- FRINGILLIDAE Common names: Scottish Crossbill; European Red List Assessment European Red List Status LC -- Least Concern, (IUCN version 3.1) Assessment Information Year published: 2015 Date assessed: 2015-03-31 Assessor(s): BirdLife International Reviewer(s): Symes, A. Compiler(s): Ashpole, J., Burfield, I., Ieronymidou, C., Pople, R., Wheatley, H. & Wright, L. Assessment Rationale European regional assessment: Least Concern (LC) EU27 regional assessment: Least Concern (LC) At both European and EU27 scales, although this species may have a small range it is not believed to approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence 10% in ten years or three generations, or with a specified population structure). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (30% decline over ten years or three generations). For these reasons the species is evaluated as Least Concern within both Europe and the EU27. Occurrence Countries/Territories of Occurrence Native: United Kingdom Population The European population is estimated at 4,100-11,400 pairs, which equates to 8,200-22,800 mature individuals. The entire population is found in the EU27. For details of national estimates, see Supplementary PDF. Trend In Europe and the EU27 the population size trend is unknown. For details of national estimates, see Supplementary PDF. Habitats and Ecology This species breeds in lowland forests and stands of Scots pine (Pinus sylvestris), including open mature plantations and ancient relict forest trees. During the winter it is mostly found in larches (Larix) and in established plantations of lodgepole pine (Pinus contorta) and sitka spruce (Picea sitchensis) as well as well- spaced pine woodland with heather (Calluna) understorey.
    [Show full text]
  • Red Crossbill
    Northeast Temperate Network National Park Service Inventory & Monitoring Program U.S. Department of the Interior ecies Red Crossbill SPotlight Loxia curvirostra 2018 marks the centennial of the Migratory Bird Treaty Act, considered by many to be the most powerful and important bird- protection law ever passed. In honor of this milestone, National Geographic, the National Audubon Society, the Cornell Lab of Ornithology, and BirdLife International are joining forces with more than 100 other organizations, including the National Park Service, and millions of people around the world to celebrate 2018 as the “Year of the Bird.” As part of this celebration, NETN’s Species Spotlight series will focus on a different bird species each month throughout the year. What is it? At first glance, it might look like this bird had a face-first, Whereas many bird species raise their chicks almost high-speed collision with a window, but its crossed bill exclusively on insects, Red Crossbills are so adapted to living is actually a finely-tuned instrument that lets it utilize an off of conifer seeds they can even be fed directly to their often plentiful, though hard to access food item. A stocky young. And the efficacy of their bills at extracting seeds from finch of mature coniferous forests, the Red Crossbill is one cones means they don’t have to wait for seed cones to open of only two crossbill species found in North America, both up on their own. This in turn allows them to breed any time of which are dependent on seed cones for their main food there is a large enough cone crop to support a flock, even source.
    [Show full text]