A preliminary study o f the feeding o f the Greenland W hite-fronted Goose Anser albifrons flavirostris in Cardiganshire

Transcription

1 108 Wildfwl A preliminary study f the feeding f the Greenland W hite-frnted Gse Anser albifrns flavirstris in Cardiganshire D. F. W. POLLARD and P. WALTERS-DAVIES Intrductin The Greenland White-frnted Gse Anser albifrns flavirstris ccurs principally in the western and nrthern areas f the British Isles. The main cncentratin is in Ireland, where perhaps threequarters f the ppulatin verwinter. The remainder inhabit remte districts f west Sctland, frm Kirkcudbright thrugh Argyll t the Outer Hebrides, apart frm smaller grups in Lancashire and Wales (Atkinsn-Willes 1963). The race is nt as well dcumented as the Eurpean White-frnted Gse A. a. albifrns n accunt f the inaccessibility f many f its haunts. The British ppulatin f A. a. albifrns represents between 12 and 20 per cent f the race, whereas that f A. a. flavirstris (including the Irish cmpnent) cmprises essentially the entire ppulatin f the race. It is mst imprtant, therefre, that knwledge f its eclgy is adequate fr a sund cnservatin plicy. Until recently, a ppulatin f abut 500 Greenland Whitefrnts verwintered at Crs Tregarn Natinal Nature Reserve in Cardiganshire. Numbers declined markedly during the severe winter f , and have rarely exceeded 100 in subsequent years. Under the directin f the Reginal Office f the Nature Cnservancy, a preliminary study f geese n the reserve was carried ut during winter In cllabratin with the Wildfwl Trust, the investigatin was intensified with a survey f vegetatin in summer 1966, based n existing knwledge f feeding habits f the geese, and was fllwed by a feeding study in winter The summer wrk was supplemented by surveys f upland bgs in the vicinity f Crs Tregarn N.N.R. which were knwn t have been frequented by Greenland Whitefrnts in previus years. Fr cmparative purpses, the prpsed nature reserve at Brth Bg, used as a feeding area by a small ppulatin f White-frnted Geese

2 f. D. H. Radfrd Plate IX. (a) A Dragn Rapide after a (rutine) landing n the sands f Barra, Outer Hebrides, during an aerial survey f Barnacle Geese. (See p. 97). (b) Ranish Island, typical winter haunt f Barnacle Geese. J. D. H. Radfrd

3 Plate Χ. Inside the new Trpical Huse at Slimbridge, (a) The general view twards the waterfall pnd, which is shwn (b) in clse-up. (See p. 169) J. A. M iddletn

4 Greenland Whitefrnts 109 reprted as A. a. albifrns, was als investigated. The first part f this paper deals with the varius surveys carried ut in Cardiganshire in summer In the secnd part, results are presented fr the preliminary feeding study f and a fd analysis scheme develped in Results are discussed in relatin t the summer investigatins. PART I. Survey f vegetatin at Crs Tregarn N.N.R. and ther sites in Cardiganshire. Study sites Crs Tregarn N.N.R. ccupies an area f 1,898 acres (769 hectares) in mid- Cardiganshire abut 12 miles (19.3 km.) frm the sea, at an altitude f abut 500 ft. (162 m.) a.s.l. The reserve is surrunded by hills up t 1,000 ft. (352 m.) a.s.l. and is centred n three adjacent raised bgs, knwn as the Western, Nrth-east and Suth-east Bgs. The bgs are separated frm each ther by prmntries f rising land and by streams flwing thrugh the reserve. These include the River Teifi and its tributaries the Camddwr and the Ffluv. These watercurses have develped narrw river terraces. A full descriptin f Crs Tregarn may be fund in Gdwin and Cnway (1939). In brief, each bg is characterized by purple mr-grass M linia caerulea at its higher levels, giving way t deer - grass Trichphrum cespitsum, pl and hummck areas (bg-mss Sphagnum spp. and cttn-grass Eriphrum spp.) and heather Calluna vulgaris. The develpment f these assciatins varies cnsiderably accrding t area, and t the extent f previus peat extractin. A peripheral zne knwn as the Rand may separate the bg frm river terrace. T the nrth, river terraces are brad and are characterized by rush Juncus and marsh willw Salix swamp. T the suth, Juncus diminishes t pasture clse t the river. The pasture is grazed by sheep and pnies. In cntrast t Crs Tregarn, Brth Bg lies almst at sea level, cvering an area f 1,352 acres (547 hectares) clse t the Dvey Estuary in nrth-west Cardiganshire. This prpsed reserve is centred n a single raised bg which is surrunded by reed Phragmites cmm unis swamp and Juncus marsh. Drainage channels include the River Leri, nw in canalised frm, and the Pwll Ddu. Other sites investigated include small upland bgs f Llyn Eiddwen, Llyn Fand, Llyn Gam Fach and Pwll-yr-uch. These bgs lie a few miles t the west f Crs Tregarn. M ethds A small number f plant species have been previusly recrded as fd surces fr A. a. flavirstris. These include deergrass Tricphrum cespitsum which was reprted by Campbell (1947) frm Whitefrnts sht in Nrth Uist, and cmmn cttn - grass Eriphrum angustiflium and white beak-sedge Rhyncspra alba which were fund in Whitefrnts sht near Crs Tregarn (Cadman 1953, 1956). Special attentin was paid t these plants in each part f the summer survey. The regin f particular interest at Crs Tregarn was the pl and hummck area f the Western Bg, since it was here that geese had been mst frequently bserved during the preliminary survey f Frequency distributin f plant species in this area was determined using 30 cm. X 30 cm. randm quadrats. A similar analysis was carried ut in the Trichphrum zne f the Western Bg, and in the pl and hummck area f Brth Bg. Surveys f the smaller bgs were limited t the cmpiling f plant species lists and general descriptin f vegetatin. The lcatin f fd parts f R h yn chspra and ther recgnised fd plants at Crs Tregarn was cnsidered in terms f depth within the substratum and its hardness. Usually, depth f fdstuff culd be measured after pulling entire plants frm the peat. Hardness f the peat was determined using a 34 cm. spear, weighing 73 g. The spear was prepared frm 5 mm. steel rd, with a filed pint and metal flights t ensure a vertical drp. Graduatins f 1 cm. were marked alng its length. The spear was drpped int sample areas frm a height f 50 cm. (frm the flights); penetratin was recrded fr 10 drps in each f 20 quadrats. Percentage cver was estimated by eye fr each plant species within quadrats. Results (a) Cmparisn f vegetatin within Crs Tregarn and Brth Bg. Frequency f species is given in Figure 1. The mst prnunced difference between pl and hummck areas f the tw raised bgs ccurred in the distributin f bg myrtle M yrica gale. This species was a prminent feature f Brth Bg but was nt bserved at Crs Tre-

5 110 Wildfwl Eriphrum angustiflium C rs T re g a r n C rs T re g a r n B rth B g 1^4 Pi an~ f-,r' ""j T ric p h ru m jn^ \ pl and hummck hummck m x m z m.i..n m π ί ί μ ς ω f t p A ndrm eda p liflia J.1.j.LJ.ti.MM! i Ín i \! fi I i E r ic a te tra lix D r se ra rtundiflia T ricph rum cae spit sum R hynchspra alb a C alluna, v u lg aris V accinium xycccus u τη.111 K W ìij.iii i ì i i n Η Μ I H M M t IT T I TL ττη 11m i tti 1.l i m!i m sn m n m K X W V v X W W W W W W W J Hü ULU...i.1.t.J ÍX D N arthecium ssifrag u m V accinium m y rtillu s E m petru m nigrum ZED XU D r se ra ln giflia 3 M y rica gale M.enyanthes trif lia ta F requen cy f ccu rren ce in th irty quad rats Figure 1. Frequency f plant species in 30 cm. X 30 cm. quadrats at Crs Tregarn and Brth Bg.

6 Greenland Whitefrnts 111 garn. Trichphrum was mre abundant at Crs Tregarn but there were n marked differences in distributin f ther fd plant species. The Trichphrum zne f Crs Tregarn is characterized by a decline in every species ther than Trichphrum and crss-leaved heath Erica tetralix. These changes reflect the drier sil cnditins as cmpared with pl and hummck areas. (b) Upland bgs in the vicinity f Crs Tregarn. Prir t winter , A. a. albifrns inhabited sme f the smaller bgs and lakes near Crs Tregarn. Of these, Llyn Eiddwen was ne f the mre frequently used. The lake is abut 500 m. lng by 250 m. wide. A small bg, extensively cut fr peat in the past, exists at the suth end. Eriphrum was very abundant, with a little Trichphrum. R h yn chspra was absent. Observatins by ne f the authrs (Pllard) in Nvember and December 1962 shwed that this bg was certainly used fr feeding by geese. Llyn Fand lies abut tw miles (3.2 km.) suth f Eiddwen; althugh similarly free frm disturbance, Llyn Fand is nt knwn t have been used by geese. This is pssibly explained by the fact that the adjacent bg cmprised essentially Juncus marsh, in cntrast t the artificial pls and hummcks in the peatcutting area f Eiddwen. Llyn Gam Fach is a very small and expsed hill tarn, n which geese are reprted t have rsted ccasinally. The surrunding bg cmprised mainly Juncus, but there was als pl and hummck develpment. Pwll-yr-uch has n permanent water but cmprises abut 10 acres f bg, much f it quaking. Eriphrum was very abundant. The bg was used by geese particularly when disturbed n Llyn Eiddwen. (c) Depth f fdstuffs in substratum. As shwn in Table I, depth f fdstuffs varied appreciably. The mst readily accessible appeared t be R h yn chspra bulbils; these were ften lcated abve the peat surface, with rts penetrating Sphagnum befre entering the peat. Depth f Eriphrum rts varied accrding t site. Only 10-15% culd be extracted with rts attached by handpulling and the frce required t lift intact plants was cnsiderable. It seems likely that this fd must be at least partly excavated by the geese a difficult prcess under freezing cnditins befre being eaten. Depth f Trichphrum sht bases varied accrding t the age f tusscks. Whilst generally quite shallw, shts f this species als were difficult t extract, wing t the frmatin f a tugh mat f fibrus rts in the tussck. (d) Hardness f substratum. Plant cver is presented diagramatically in Figure 2 fr each f fur classes f peat hardness, as indicated by mean depth f penetratin f the spear described abve. Certain species shwed a distinct crrelatin with hardness f substrate. Thus, Sphagnum species were cnsiderably mre abundant in sfter areas. R hynchspra appeared t grw mainly in areas f Table I. Depth f sht base in varius plant species n Crs Tregarn. Av. depth Standard Species and parts eaten Site (cm.) errr Substratum level White beak-sedge (bulbils) Shallw pls Peat surface Rhynchspra alba Wet Sphagnum Sphagnum, upper surface C alluna/erica assc Peat surface Cmmn cttn-grass (rts) Shallw pls Peat surface Eriphrum angustiflium Wet Sphagnum Sphagnum, upper surface Drier Sphagnum Sphagnum, upper surface Calluna/Erica assc Peat surface Deer-grass (bulbils) Old tusscks Tussck surface Trichphrum cespitsum Yung tusscks Tussck surface

7 112 Wildfwl O) e <D Mcö 30 <D c 2 0 cö Jh CD > O u i J Figure 2. Plant cver in relatin t hardness f substratum. intermediate hardness, nt tlerating the very sft ze in pls. (At Brth Bg it was abundant in firm and cmparatively dry peat f ld peat-cutting and fire znes. Apparently this species, a clniser f pls n the raised bg, tlerates harder peat in the absence f strng cmpetitin frm species such as Calluna, Erica and white frk mss Leucbryum glaucum.) Eriphrum shwed a brad tlerance range; Trichphrum was cnfined mainly t firmer areas. Resistance t penetratin in tusscks was cmparable t that f hard-packed peat. PART II. Studies in feeding habits f Greenland White-frnted Geese in Cardiganshire. Backgrund The fact that A. a. flavirstris was nt recgnised as distinct frm A. a. albifrns until cmparatively recently (Dalgety and Sctt 1948) cmplicates evaluatin f earlier feeding studies n White-frnted Geese. Campbell (1947) reprted tw instances f bulbils f Trichphrum fund in the crps f Greenland Whitefrnts sht in Nrth Uist. The nly ther recrds are in Cadman (1953, 1956) wh fund rts f Eriphrum and yung

8 Greenland Whitefrnts 113 shts f Rhynchspra in viscera f geese sht in the vicinity f Crs Tregarn. Each f these recrds refer t material cllected thrugh viscera analysis f sht birds. The technique f viscera analysis fr investigatin f wildfwl feeding habits has been described by Harrisn (1960) and has been used extensively in studies f several species f duck, e.g. Olney (1964). Generally, hwever, viscera analysis may be used nly fr quarry species, since the researcher is usually dependent n wildfwlers fr the supply f study material. Whilst A. a. flavirstris is n the shting list, its distributin is such that much f the British ppulatin is affrded prtectin thrugh remteness r preservatin f its wintering areas. In additin t difficulties in btaining material frm such lcatins, it is undesirable that further reductin f a small ppulatin shuld ccur thrugh such sampling techniques. An alternative apprach t wildfwl fd analysis was adpted by Ranwell and Dwning (1959) in a study f feeding pattern in Brent Geese Branta bernicla. Faeces f this species were fund t be suitable fr fd determinatin thrugh micrscpic examinatin f plant remains. This technique had already fund applicatin in feeding studies f rabbits (Dusi 1949) and has been frequently emplyed in investigatins f range habits f herbivres (Stewart 1967). Faeces analysis ffers the special advantage in wildfwl feeding studies that the size, number and frequency f samples is limited nly by the amunt f disturbance impsed n the birds in cllecting material. It is therefre very suitable in situatins where cnservatin f the lcal ppulatin is f special imprtance, and where access is fully cntrlled. Fr this reasn, faeces analysis was emplyed fr the feeding study f A. a. flavirstris at Crs Tregarn Natinal Nature Reserve. M ethds The preliminary study f was based n direct bservatins by the previus Warden-Naturalist, Mr. P. J. Panting. On each f 23 ccasins, a nine mile (14 km.) transect abut 400 yards (370 m.) wide was surveyed. Date f bservatin and lcatin f grups f feeding birds were recrded n a largescale map f the reserve. In preparatin fr the feeding study f , samples f knwn fd plant parts, and material f assciated plant species, were gathered in late autumn Permanent munts f sectins shwing diagnstic features within the upper and lwer epidermal surfaces were prepared by the methd utlined by Metcalfe (I960), fr reference purpses in subsequent micrscpic examinatin f faeces. The reference cllectin was supplemented by material gathered during winter Cllectin f faeces cmmenced immediately after the arrival f geese in Octber Thirty faeces were cllected by the Warden-Naturalist, Mr. P. Davis, at apprximately three-week intervals, and were immediately despatched t the Wildfwl Trust fr analysis. Upn arrival, six were randmly selected frm the sample and sealed individually in tubes cntaining frmal acetic acid (FAA). The frequency f sampling was increased in March 1967 when changes in cmpsitin f the drppings were bserved. Cllectin and subsampling prcedures were such that it culd be reasnably assumed that each drpping riginated frm a different bird. Faeces were prepared fr analysis by crushing in FAA a few days after fixing. Separatin f plant fragments was fund t be facilitated by the fixing prcedure. Ten prtins f slurry frm each faeces were examined fr cmpnent plant species. Presence r absence nly was resrted t after attempts t quantify the ccurrence f each species prved unsatisfactry. Results (a) Preliminary survey Lcatins f feeding geese during are shwn in Figure 3(i) in relatin t minimum grund temperature as recrded fr the preceding 24 hurs at Swyddffynn meterlgical statin n the edge f Crs Tregarn N.N.R. In a ttal f 23 bservatins, geese were feeding n raised bg n 19 ccasins, and n pasture (mainly river terrace) n 13 ccasins. Birds were seen in bth areas n 10 days, indicating mvement r splitting f the flck. There was an increase in use f pasture after Nvember; in general, feeding statin did nt appear t be assciated with temperature. (b) Drppings analysis and direct bservatins, Faeces analyses resulted in strikingly few species being identified as fd plants and fr much f the winter feeding appeared t be cnfined t bulbils f Rhynchspra alba. It shuld be nted, hwever, that geese and fresh drppings culd nt always be lcated within the reserve (hence the irregularity f

9 114 Wildfwl '-1 50 'Pt u 10 0 (i) Oct (ii) O Nv Raised bg: direct bservatin ö > faecal analysis Δ Pasture: II 11 it n Jan Feb Mar Apr 50 1ΞΓ 40 Am "7 30 S 20 Ό 10 O Δ. Δ Ο O 0 Oct Nv Dec Jan Feb Mar Apr Figure 3. Lcatin f feeding geese in relatin t grund temperature, Crs Tregarn, and samples); since Rhynchspra appeared t be cnfined t Crs Tregarn in that particular regin, it is mst unlikely that the diet f geese was as unvaried as is suggested. Nt until the middle f March did sample drppings cntain species ther than Rhynchspra. In every case, identifiable drppings cntents reflected thse species ccurring in the area frm which the sample was cllected. In late March and April, the mst cmmn material in drppings was fliage f cmmn bentgrass Agrstis tenuis. This was als the mst abundant species in the turf f river terraces. Reed-grass Glyceria spp., cmmn in wetter sectins f terraces, was detected. Tufted hair-grass Deschampsia cespitsa was taken frequently twards the time f departure f the geese (18th April 1967), and in tw instances cmprised ver 50% f drppings material. Dictylednus fliage ccasinally frmed a substantial prprtin f drppings frm river terraces, but culd nt be identified further. Direct bservatins n feeding geese fr winter are shwn in Figure 3(ii). Prir t mid-march, birds were bserved feeding n pasture n nly three ccasins; there was n indicatin f a temperature effect n feeding statin. Direct bservatin supprted the evidence frm drppings analysis f a change in feeding habits in mid-march. In , pasture grazing was frequent thrughut the winter. Feeding pattern in late March and April f that year culd nt be bserved due t earlier departure f the geese. Discussin There is litde dubt that the drastic decline in the ppulatin f A. a. flavirstris at Crs Tregarn in winter was assciated with the very severe cnditins at that time. Markgren and Mathiassn (1963) cncluded that premature departure frm feeding grunds under adverse cnditins reflected limited fd supplies rather than a direct respnse t the weather. Hwever, the reductin in numbers at Crs Tregarn was permanent, and is believed t have resulted frm the cmbined effects f starvatin and shting. In n geese were bserved n the area (P. Davis, pers, cm.). By virtue f its status as a Natinal Nature Reserve, Crs Tregarn affrds cmplete prtectin f its fauna and flra (sectin 16, Natinal Parks and Access t the Cuntryside Act 1949). In the case f a quarry species such as A. a. flavirstris, hwever, prtectin is limited t the scheduled area f the reserve. Under nrmal cnditins, the species fed within this area fr much f the winter, as in-

10 Greenland Whitefrnts 115 dicated by bservatins in and , althugh visits t remte upland bgs were nt unusual in previus years. Hwever, in geese mved ut f the reserve int agricultural areas, presumably in search f fd, and in cnsequence were subject t unusual shting pressure. Accrding t bservatins reprted in this and ther papers (see abve) the fd plants f A. a. flavirstris include Eriphrum angustiflium, Rhynchspra alba, Trichphrum cespitsum and a number f grasses f which Agrstis tenuis, Deschampsia cespitsa, Yrkshire fg Hlcus lanatus and Glyceria spp. appear t be imprtant. Study f distributin f the first three fdstuffs in peat at Crs Tregarn suggested that Eriphrum rts wuld be the least available under severe cnditins. Deschampsia bulbils wuld prbably be available even with deep snw cver, but there are n recrds f these being cnsumed by geese in Cardiganshire. Rhynchspra bulbils ccur at very shallw levels and are ften develped within the verlying Sphagnum. Even under very cld cnditins, this fd wuld still be available, and culd be readily btained during perids f snw cver. Cadman (1956) reached similar cnclusins. In , and prbably in als, Rhynchspra was an imprtant fd frm the time f arrival f the geese until shrtly befre their departure in spring. Eriphrum was nt detected in any drppings samples analysed. Bth drppings analysis and direct bservatins made n the reserve als indicated that pasture was an imprtant surce f fd. There is als a substantial unknwn element in the winter nutritin f these geese. There appears t be n reliable infrmatin n the lcatin and feeding habits f the birds when nt within the cnfines f Crs Tregarn N.N.R., apart frm bservatins made n the larger ppulatin prir t (Cadman 1953, 1956). There was a prnunced change in feeding pattern shrtly befre departure f geese in April 1967, when feeding tk place predminantly n grasses (river terrace) instead f Rhynchspra (raised bg). (It is interesting t nte that geese were claimed by lcal farmers t be f cnsiderable nuisance n early pasture grass and winter wheat when the ppulatin numbered several hundred.) The reasns fr this change are bscure. Pssibly changes ccurred in the nutritive value f either fd items, fr example, a lwer prtein cntent in rapidlyexpanding Rhynchspra bulbils, r an increasing prtein level in grasses. In an investigatin f A. a. albifrns at Slimbridge, Glucestershire, Kear and Pllard (unpublished) fund substantial increases in prtein levels in the early spring f 1966, nt nly in grass fliage extracted frm viscera, but als in drppings and randm clips frm the feeding area. A similar increase in the use f uncultivated grassland in early spring was bserved by Markgren and Mathiassn (1963) in a study f Bean Geese Anser fabalis. These authrs als fund Deschampsia cespitsa t be an imprtant fd plant f this species in sme lcalities. The increasing frequency f Deschampsia utilizatin at Crs Tregarn twards the time f departure in 1967 is especially interesting, since it is generally regarded as being a pr surce f fd fr herbivres. The nly knwn majr surces f Rhynchspra in nrth-west Cardiganshire are Crs Tregarn and Brth Bg. Feeding areas and habits f the ppulatin f A. a. albifrns at Brth Bg have nt been fully investigated, but mst reprts suggest that feeding ccurs in the Trichphrum and peat-cutting znes at the suth end. Hwever, these geese have als been bserved feeding n grazed pasture in January and March 1967 and, smewhat surprisingly, n mud within the tidal zne f the Dvey estuary, which was later shwn t hld quantities f crustaceans Gammarus sp. and mlluscs Hydrbia sp. Despite the similarities between available feeding grunds at Brth Bg and Crs Tregarn as shwn frm the summer surveys f 1966 there has been n indicatin that geese frm the latter site use Brth Bg as an alternative feeding area. Acknwledgements The authrs wish t express their gratitude t Mr. P. Davis fr his help in cllecting material and recrding bservatins at Crs Tregarn, Mr. P. Panting fr his assistance in and Mr. E. D. Williams fr his bservatins n upland bgs near Tregarn. Dr. G. V. T. Matthews, Dr. D. S. Ranwell and Mr. H. Byd prvided useful criticism f the draft paper. Appreciatin is als extended t the Nature Cnservancy in prviding access and labratry facilities fr the summer survey f Crs Tregarn. The 1966 summer survey and

11 116 Wildfwl and was grant-aided by the Natural En virnment Research Cuncil. feeding investigatin was carried ut under the auspices f the Wildfwl Trust, Summary An investigatin f feeding habits f Greenland White-frnted Geese Anser albifrns flavirstris in Cardiganshire was cmmenced in winter , fllwing a drastic decline in the ppulatin in A survey f feeding grunds was made in summer 1966, fllwed by an intensive study f feeding habits in winter , in which the technique f faeces analysis was emplyed. During much f the winter the preferred fd plant species taken at Crs Tregarn was white beak-sedge Rhynchspra alba. Varius grass species were als taken, particularly in spring. Temperature did nt appear t be an imprtant factr f feeding pattern, althugh there were indicatins that certain fdstuffs wuld nt be readily available under severe cnditins. The technique f faeces analysis is discussed in relatin t research int feeding habits f disturbance-sensitive species. References At k in s n -Wil l e s, G. L. (Ed.) Wildfwl in Great Britain. Nature Cnservancy Mngraph N. 3. Lndn : H.M.S.O. c a d m a n, w. a The winter fd and eclgical distributin f Greenland Whitefrnted Geese in Britain. Brit. Birds 46 : cadm an, w. a The wildfwler naturalist. Nature in Wales 2 : Ca m p b e l l, J. w The fd f sme British waterfwl. Ibis 89 : DALGETY, c. τ. and p. s c t t A new race f White-frnted Gse. Bull. B.O.C. 68 : d u s i, J. L Methds fr the determinatin f fd habits by plant micrtechniques and histlgy and their applicatin t cttntail rabbit fd habits. J. Wildl. Mgmt. 13 : G d w in, H. and v. m. c n w a y Eclgy f a raised bg near Tregarn, Cardiganshire. J. Ecl. 27 : MARKGREN, G. and s. m a t h ia ss n Studies n wild geese in suthernmst Sweden. Acta Vertebratica 2 : m e t c a l f, C. R Anatmy f the Mnctyledns. I. Graminae. Oxfrd : Clarendn Press. l n e y, p. j. s The fd f Mallard Anas p. platyrhynchs cllected frm castal and estuarine areas. Prc. Zl. Sc. Lndn 142 : r a n w e l l, d. s. and B. Μ. d w n in g Brent gse (Branta bernicla (L.)) winter feeding pattern and Zstera resurces at Sclt Head Island, Nrflk. Animal Behaviur 7 : S t e w a r t, D. R. Μ Analysis f plant epidermes in faeces: a technique fr studying the fd preferences f grazing herbivres. J. Appi. Ecl. 4 : Dr. D. F. W. Pllard, Petawawa Frest Experiment Statin, Chalk River, Ontari, Canada. P. Walters-Davies, Reginal Officer, The Nature Cnservancy, Aberystwyth, Cardiganshire.