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[Predation of sheep on wild bird eggs and chicks in Iceland.]

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Abstract

In 2019 to 2021 sheep were noted eating Arctic tern Sterna paradisaea eggs, as well as beheading chicks and cutting off part of their wings, on the island of Flatey in Breiðafjörður, W-Iceland (Figs 1–5). One Redshank chick Tringa totanus was also found beheaded. The reason for this behaviour is unknown but may possibly be related to mineral deficiency in the sheep. Recorded observations of this kind are rare in Iceland. Here is a summary in chronological order of other incidental observations when livestock were either seen or inferred to have taken wild bird eggs or killed unfledged young. The first such observation is from 1964 when sheep were seen eating Arc tic tern eggs on the island of Flatey in Skjálfandi bay, N-Iceland. The second example is from 1983−1985 when domestic sheep were observed predating on various wader eggs, such as Golden Plover Pluvialis apricaria and Whimbrel Numenius phaeopus at the farm Engidalur in N-Iceland. The third example is from 1996 when sheep in Mjóifjörður, E-Iceland, were inferred having predated Arctic tern chicks, which were found head less and some of the sheep in same enclosure were found to have blood on their muzzle. During 2010–2013, in a breeding biology study of Whimbrel in S-Iceland, using camera traps, sheep and horses were recorded predating eggs. The effects of sheep or other live stock on wild birds is still poorly stud ied in Iceland, but these can be both negative and positive for the birds.
Náttúrufræðingurinn
132
Sauðfé étur
kríuegg og unga
Ævar Petersen, Sverrir Thorstensen, Scott Petrek og Kane Brides
SUMARIÐ 2019 sást til kinda í Flatey á Breiðafirði sem ýttu kríu Sterna paradisaea
af hreiðri sínu og átu síðan egg hennar. Síðar sama sumar fundust ði lifandi og
dauðir kríuungar með hluta vængjar eða allan vænginn afstýfðan, svo og dauðir haus-
lausir ungar. Fyrstu dauðu kríuungarnir fundust um miðjan júlí. Einnig fannst hauslaus
stelksungi og ðar fleiri kríuungar. Alls fundust 17 hauslausir og vængstýfðir kríuungar
þetta sumar. Kindur voru rétt hjá en engir aðrir hugsanlegir orsakavaldar. Sumrin 2020
og 2021 fundust einnig dauðir hauslausir ungar og lifandi ungar sem á vantaði hluta
vængjar. Hér segir nánar frá þessu og rifjuð eru upp önnur tilvik hér á landi sem okkur
eru kunnug um kindur sem urðu uppvísar að eggja- eða ungaáti.
1. mynd. Ær með tvö lömb við kríu á hreiðri. Rétt eftir að myndin var tekin sást annað lambið hnippa
í fuglinn og kasta honum af hreiðrinu. Síðan átu kindurnar eggin. Myndin er tekin á Pálsvelli í Flatey á
Breiðafirði. – Ewe with her two lambs at an Arctic tern nest. Just after this photo was shot one of the
lambs tossed the adult tern off the nest with its muzzle and the eggs were eaten. Flatey in Breiðafjörður.
Ljósm./Photo: Kane Brides, 11.06.2019.
Náttúrufræðingurinn 91 (3–4) bls. 132–137, 2021
Tímarit Hins íslenska náttúrufræðifélags
133
Lundabergsmóar
Mjósund
Flugvöllur
Steinabrekka
Klausturhólamýri
Pálsvöllur
Alheimsmýri
Innstabæjarmýri
INNGANGUR
Búfénaður hefur ði bein og óbein
áhrif á villta fugla, útbreiðslu þeirra
og fjölda.1,2 Þrátt fyrir það virðast litlar
rannsóknir hafa farið fram á þessum
áhrifum hér á landi, sem geta verið
margvísleg og flókin. Bein áhrif eru
meðal annars dráp á fuglum og eggjaát.
Þá getur búfé troðið niður hreiður eða
lagst á hreiður óafvitandi. Óbein áhrif
geta verið breytt gróðurfar vegna beitar,
sem hefur áhrif á fuglalíf.
Einn þáttur í samskiptum búfénaðar
og villtra fugla er afrán af völdum sauð-
fjár. Hér á landi hafa örfá tilvik verið
skráð um slíkt afrán en ætla má að það
sé algengara en þau tilvik sýna. Afrán
sauðfjár á eggjum og ungum villtra fugla
er einnig þekkt erlendis.3,4
Hér er skýrt frá tilvikum þar sem
ljóst er að kindur hafa étið egg og unga
kríu Sterna paradisaea í Flatey á Breiða-
firði, og öðrum stöðum á landinu sem
við höfum spurnir af.
ATHUGANIR
Kríuvarpið í Flatey hefur tekið tals-
verðum breytingum á undanförnum
áratugum. Á árunum 1975 til 1978 urpu
um 2.000 kríupör í eynni.5 Árið 1990
hafði þeim fjölgað í 3.000 pör en síðan
fækkaði þeim á ný og á árunum 2009
til 2016 var fjöldinn breytilegur, frá um
500 til 1.500 pör.6
Flatey 2019
Sumarið 2019 urðum við vitni að þ
að ær og tvö lömb hennar umkringdu
kríu á hreiðri (1. mynd). Fuglinn sat sem
fastast uns annað lambið hnippti í hann
þannig að krían þeyttist af hreiðrinu og
tók flugið. Tóku kindurnar sig þá til og
átu eggin. Á meðan renndi fuglinn sér í
kindurnar eins og kríur eiga vanda til en
þær létu ekki segjast.
Ýmis örnefni í Flatey sem nefnd eru í
greininni má sjá á 2. mynd.
Sumarið 2019 var fylgst með kríu-
varpi í 10 daga á svæði þar sem kindum
var haldið til beitar (Pálsvöllur
Innstabæjarmýri). Áberandi var hve
kríum og hreiðrum þeirra fækkaði ört
á þessum tíma. Hinum megin girðingar
(í Klausturhólamýri) voru engar kindur.
Varpárangur þar var metinn sumarið
2019. Hann reyndist óvenjugóður (1,1
ungi á hreiður þegar ungar voru komnir
rétt undir flug) og engin merki sáust um
afrán (ÆP & ST, óbirt gögn). Í rannsókn
á kríuvarpi á Snæfellsnesi 2008–2011
voru sambærilegar tölur 0,05 til 0,51.7
Fyrstu merki um hauslausa unga
eru frá 17. júlí 2019. Þá fundust fimm
kríuungar og einn stelksungi Tringa
totanus á Lundabergsmóum og flug-
velli austur að Mjósundum. ðar um
sumarið fundust lifandi kríuungar sem
á vantaði hluta af væng (3. mynd). Þetta
var í sama beitarhólfi og kindur sáust
éta egg fyrr um sumarið.
2. mynd. Flatey á Breiðafirði. Örnefni sem nefnd eru í greininni. – Flatey in Breiðafjörður.
Local names mentioned in the Icelandic text.
Náttúrufræðingurinn
134
Einnig fundust tveir nýdauðir haus-
lausir ungar á svæði sem hafði verið
skoðað um hálftíma áður án þess að
dauðir ungar sæjust (4. mynd). Rétt áður
sáust kindur á nákvæmlega sama stað.
Engar líkur eru á að fuglarnir hafi misst
væng eða haus við það að fljúga á raf-
magnsvíra eða girðingar enda ungarnir
enn ófleygir. Hauslausu ungarnir voru
sumir nýdauðir; blóð lak úr strjúpanum
eða var nýstorknað. Ummerkin voru eins
og vængur eða haus hefðu verið rifnir
frá búknum.
Flatey 2020
Kindur sáust ekki éta kríuegg í júní
2020. Hins vegar var áberandi þá tíu
daga sem dvalist var í Flatey hve kríum
með hreiður fækkaði mikið á sama
svæði og kindur sáust éta egg og væng-
stýfðir eða hauslausir ungar fundust
sumarið áður.
Í júlí 2020 fundust fimm vængstýfðir
ungar og sjö hauslausir á sama svæði
og sumarið 2019, þ.e. á Pálsvelli og í
Innstabæjarmýri.
Þrjú kríuhreiður voru í Steinabrekku
á Flatey 5. júní 2020. Fylgst var með
hreiðrunum daglega og 10. júní var eitt
hreiður eftir með eggjum. Nokkrum
kindum var haldið til beitar í hólfi á
þessu svæði og er talið að þær hafi étið
eggin úr tveimur hreiðranna. Kindurnar
sáust iðulega fast við hreiðrin og létu
sér fátt um finnast þegar kríurnar tóku
dýfu niður að þeim og hjuggu þær
jafnvel í hausinn.
Flatey 2021
Í júlí 2021 fannst stakur ungi í Al-
heimsmýri. Hafði hausinn verið stýfður
af og var strjúpinn alblóðugur. Greini-
legt var að unginn hafði verið drepinn
rétt áður (5. mynd). Unginn fannst alveg
við girðinguna við Pálsvöll þar sem
ungar fundust afhausaðir á fyrri árum.
Kindur voru stutt frá og var ekki hægt
að draga aðra ályktun en að þær hefðu
bitið í haus kríuungans og dregið fram
af hálsinum.
Flatey almennt
Hér er einungis um stök tilvik
að ða og lítið vitað um áhrif á
fuglastofna, dreifingu þeirra eða varp-
árangur eftir svæðum, enda ekki sér-
staklega verið að fjalla um samspil
sauðfjár og fugla. Þrátt fyrir áratuga-
rannsóknir á fuglum í Flatey hefur ekki
áður orðið vart við kindur éta egg eða
unga, meðal annars á þeim svæðum
sem getið er að ofan. Sauðfé gengur
um nær alla ey núorðið, meðal annars
ða þar sem er æðarvarp, nema hvað
túnum (nýræktum) á austurhluta eyj-
unnar er haldið fjárlausum. Áður fyrr,
3. mynd. Í Flatey á Breiðafirði. Kríuungi sem
búið er að bíta af hálfan vænginn. – Arctic tern
chick with half of the wing cut off. Flatey in
Breiðafjörður. Ljósm./Photo: Ævar Petersen,
23.07.2019.
4. mynd. Hauslausir kríuungar í Flatey á Breiðafirði. Sést í blóðugan strjúpann. – Be-
headed Arctic tern chicks, with bloody neck. Flatey in Breiðafjörður. Ljósm./Photo:
Ævar Petersen, 23.07.2019.
Tímarit Hins íslenska náttúrufræðifélags
135
5. mynd. Afhausaður kríuungi. Fundinn nýdauður í Alheimsmýri í Flatey á Breiðafirði.
– Arctic tern chick that had been beheaded, found newly dead. Flatey in Breiða-
fjörður. Ljósm./Photo: Ragnar Helgi Ólafsson, 19.07.2021.
þegar sauðfé Flateyjarbænda var tölu-
vert fleira, voru kindurnar fluttar úr
eynni og upp á land áður en langt var
liðið á sumar. Vissulega hafa kríu-
ungar margoft fundist dauðir af öðrum
orsökum í kríuvarpinu í Flatey.5
ÖNNUR TILVIK Á LANDINU
Okkur er kunnugt um fjögur tilvik
annars staðar af landinu þar sem sauð
át egg eða unga villtra fugla.
1. Flatey á Skjálfanda,
Suður-Þingeyjarsýslu.
Stórt kríuvarp hefur lengi verið í
Flatey á Skjálfanda.8 Árið 1964, þegar
þar var ennþá heilsársbyggð, varð fólk
vart við hauslausa kríuunga. Vegsum-
merki voru alveg eins og lýst hefur verið
í Flatey á Breiðafirði, þ.e. hausinn virtist
hafa verið slitinn eða bitinn af, og voru
kindur þar staðnar að verki.9
2. Engidalur, Bárðardal,
Suður-Þingeyjarsýslu.
Kristlaug Pálsdóttir í Engidal hefur
merkt fugla um langt árabil, ekki síst
vaðfuglaunga. Hún var mikið á ferli
um móana og fann þá mörg hreiður
vaðfugla, svo sem heiðlóu Pluvialis
apricaria og spóa Numenius phaeopus.
Hafði hún auga með hvenær ungar
skriðu úr eggjum og merkti þá áður en
þeir yfirgáfu hreiðrið. Á árunum 1983–
1985 tók Kristlaug eftir þþegar hún
var að reka kindur að sumar þeirra tóku
á rás að stöðum þar sem fuglar flugu
upp, leituðu að eggjum og átu. Kristlaug
greinir frá þessu í tímaritinu Blika.10
3. Hesteyri, Mjóafirði, Austfjörðum.
Árið 1996 (6. júlí) voru Þórey Ketils-
dóttir, Sólveig Bergs og tveir höfunda
(ST og ÆP) að merkja kríuunga við
Hesteyri í Mjóafirði á Austfjörðum.
Fyrst fóru merkingar fram utan tún-
girðingar í nánd við bæinn en síðar
var leitað inn á túnið þar sem var
talsvert kríuvarp en einnig sauð
á beit. Þar fundust fjölmargir haus-
lausir kríuungar og var varla hægt að
draga aðra ályktun en þá að kindurnar
hefðu drepið ungana. Þó komu hundar
einnig til greina. Þórey ræddi við ábú-
anda jarðarinnar, Önnu Mörtu Guð-
mundsdóttur, sem bjó ein á bænum
(sjá ævisögu hennar eftir Rannveigu
Þórhallsdóttur11). Anna átti tvo hunda
en sagði þá aldrei hlaupa um túnin
eftir kindunum. Þegar henni var sagt
frá dauðu kríuungunum sagði Anna að
þar væri komin skýring á það sumar
kindur hennar væru blóðugar um
kjammann.
Náttúrufræðingurinn
136
4. Suðurland.
Við rannsóknir á spóum á Suðurlandi
2010–2013 kom í ljós afrán bæði kinda
og hesta á eggjum fuglanna. Þetta sást
glögglega í myndavélum sem settar voru
upp í grennd við hreiður. Niðurstaðna
er getið í að minnsta kosti þremur rit-
gerðum og einu ðstefnuspjaldi þar
sem fjallað er um varpárangur spóa og
hverjir væru valdir að eggjahvarfi.1215
UMRÆÐA
Eflaust eru tilvik um eggja- eða ungaát
sauðfjár fleiri en hér eru tilgreind
þótt þau hafi ekki verið skráð eða
okkur kunnugt um þau. Fækkun í vað-
fuglastofnum í Evrópu hefur verið
tengd við tap á kjörlendum þeirra vegna
landbúnaðar.16 Sjófuglar verða einnig
fyrir barðinu á búfénaði.3,4 Sama á við
hér á landi.
Hvers vegna étur sauðfé egg
og unga villtra fugla?
Óljóst er hversu ðtækt það er að
sauðéti egg eða unga. Ef til vill hafa
einungis ákveðnar kindur tekið upp á
þessu atferli á svipaðan hátt og einstaka
svartbakar Larus marinus taka æðar-
unga Somateria mollissima. Þeir koma
sér fyrir á útsýnisstað og hafa vakandi
auga með æðarkollum með unga.17
Sú skýring hefur verið nefnd á fugla-
áti kinda að þær vanti steinefni.3 Í Flatey
þar sem vart varð við eggja- og ungaát
voru kindurnar í girðingu og komust
ekki í fjöru. Kindur í Breiðafjarðareyjum
hafa löngum leitað í fjörubeit þar
sem þær innbyrða salt með þangi.18,19
Sauð getur einnig vantað steinefni
vegna þess að þer haldið á of litlum
afgirtum svæðum. Það virðist samt ekki
vera algild skýring enda sést sauðfé oft
á þðvegum landsins sleikja salt sem
notað er til rykbindingar á malarvegum,
en vegsalt er að mestu natríumklóríð,
þ.e. venjulegt matarsalt.20
Búfé getur haft ýmis önnur áhrif á
villta fugla en að éta egg og unga. Þannig
eru hreiður troðin niður og egg brotin.21
Samband er á milli áhrifa á fugla og
fjölda húsdýra, og hversu lengi dýrin
eru í ákveðnu hólfi.1,22 Varp mófugla, svo
sem hrossagauka Gallinago gallinago í
Flatey misferst iðulega vegna átroðn-
ings, eins og fjölmargar skráningar vitna
um (ÆP & ST, óbirtar uppl.).
Áhrif búfjár eru eflaust breyti-
leg eftir þhvaða búfénaður á í hlut.
Þannig gengur hrossabeit oft nærri
landi í litlum beitarhólfum. Sýnt hefur
verið fram á að varpþéttleiki vepju
Vanellus vanellus er ekki eins mikill þar
sem búfénaði er beitt og meiri hætta
er á afráni.23 Hér er ekki svigrúm til
að kafa djúpt í þetta viðfangsefni en
full ástæða er til að benda á að áhrif
búfénaðar á fugla eru enn lítt könnuð
á Íslandi.2427 Þau geta bæði verið nei-
kvæð og jákvæð.
SUMMARY
Predation of sheep on wild bird
eggs and chicks in Iceland
In 2019 to 2021 sheep were noted eat-
ing Arctic tern Sterna paradisaea eggs,
as well as beheading chicks and cutting
off part of their wings, on the island
of Flatey in Breiðafjörður, W-Iceland
(Figs 1–5). One Redshank chick Tringa
totanus was also found beheaded. The
reason for this behaviour is unknown
but may possibly be related to minieral
deficiency in the sheep.
Recorded observations of this kind
are rare in Iceland. Here is a summary in
chronological order of other incidental
observations when livestock were either
seen or inferred to have taken wild bird
eggs or killed unfledged young.
The first such observation is from
1964 when sheep were seen eating Arc-
tic tern eggs on the island of Flatey in
Skjálfandi bay, N-Iceland.
The second example is from
19831985 when domestic sheep were
observed predating on various wader
eggs, such as Golden Plover Pluvia-
lis apricaria and Whimbrel Numenius
phaeopus at the farm Engidalur in
N-Iceland.
The third example is from 1996
when sheep in Mjóifjörður, E-Iceland,
were inferred having predated Arctic
tern chicks, which were found head-
less and some of the sheep in same
enclosure were found to have blood on
their muzzle.
During 2010–2013, in a breeding
biology study of Whimbrel Numenius
phaeopus in S-Iceland, using camera
traps, sheep and horses were recorded
predating eggs.
The effects of sheep or other live-
stock on wild birds is still poorly stud-
ied in Iceland, but these can be both
negative and positive for the birds.
1. Beintema, A.J. & Müskens, G.J.D.M. 1987. Nesting success of birds breeding in
Dutch agricultural grasslands. Journal of Applied Ecology 24(3). 743–758.
2. Sharps, E., Smart, J., Mason, L.R., Jones, K., Skov, M.W., Garbutt, A. & Hiddink,
J.G. 2017. Nest trampling and ground nesting birds: Quantifying temporal and
spatial overlap between cattle activity and breeding Redshank. Ecology and
Evolution 7(16). 6622–6633.
3. Furness, R.W. 1988. The predation of tern chicks by sheep. Bird Study 35(3).
199–202.
4. Furness, R.W. 1988. Predation on ground-nesting seabirds by island populations
of red deer Cervus elaphus and sheep Ovis. Journal of Zoology 216(3). 565–573.
5. Ævar Petersen 1979. Varpfuglar Flateyjar á Breiðafirði og nokkurra nærliggj-
andi eyja. Náttúrufræðingurinn 49(23). 229256.
HEIMILDIR
ÞAKKIR
Ragnar Helgi Ólafsson lagði til mynd sem höfundar þakka fyrir.
6. Ævar Petersen 2018. Arctic ter ns in Iceland. F yrirlestur 13. m ars 2018 á fundinum
CBird meeting í Cambridge, Englandi. 21 bls. https://www.researchgate.
net/publication/356504421_erindi-2018-03-13-Kria-CBird_22_-Cambridge
7. Freydís Vigfúsdóttir, Tómas G. Gunnarsson & Gill, J.A. 2013. Annual and
between-colony variation in productivity of Arctic tern in West Iceland. Bird
Study 60(3). 289297.
8. Ævar Petersen 2010. Fuglalíf í Flatey á Skjálfanda. Náttúrufræðistofnun Íslands
NÍ-10001, Reykjavík. 44 bls.
9. Sigurður Gunnarsson 2000. Höfuðlausir kríuungar. Bliki 20. 65.
10. Kristlaug Pálsdóttir 1992. Eggjaát hjá kindum. Bliki 12. 55–56.
11. Rannveig Þórhallsdóttir 2008. Ég hef nú sjaldan verið algild. Hólar, Akureyri.
279 bls.
12. Borgný Katrínardóttir 2012. The importance of Icelandic riverplains as breed-
ing habitats for Whimbrels Numenius phaeopus. MS-ritgerð við Háskóla
Íslands. 50 bls.
13. Tómas G. Gunnarsson & Borgný Katrínardóttir 2014. Sauðfé étur egg og unga.
Bændablaðið 20. nóvember, 51.
Tímarit Hins íslenska náttúrufræðifélags
137
Ævar Petersen (f. 1948) lauk BS-Honours-prófi í dýra-
fræði frá Aberdeen-háskóla í Skotlandi 1973 og dokt-
orsprófi í fuglafræði frá Oxford-háskóla á Englandi 1981.
Ævar er nú á eftirlaunum.
Sverrir Thorstensen (f. 1949) lauk kennaraprófi 1970.
Hann var kennari og skólastjóri í Stórutjarnaskóla í
Ljósavatnsskarði og síðan kennari í Glerárskóla á Akur-
eyri en er nú á eftirlaunum. Sverrir hefur stundað merk-
ingar og rannsóknir á fuglum frá árinu 1979.
Scott Petrek (f. 1989) er Breti sem unnið hefur að nátt-
úruverndarmálum frá 17 ára aldri. Hann vinnur nú við
stjórnun verndarsvæðis, m.a. að endurbótum kjörlenda
fyrir fugla, móttöku gesta og vöktun fuglastofna. Stundar
ennfremur fuglamerkingar og aðstoðar við rannsóknir á
vaðfuglum og öðrum votlendisfuglum.
Kane Brides (f. 1989) er breskur vistfræðingur sem sér-
hæfir sig í stofnvöktun votlendisfugla, vistfræði þeirra
og farháttum.
UM HÖFUNDA
PÓST- OG NETFÖNG HÖFUNDA
/ AUTHORS' ADDRESSES
Ævar Petersen
Brautarlandi 2
IS-108 Reykjavík
aevar@nett.is
Sverrir Thorstensen
Lönguhlíð 9a
IS-603 Akureyri
sth@akmennt.is
Scott Petrek
WWT Slimbridge Wetland Centre
Slimbridge, Glos, GL2 7BT
UK Bretlandi
scott.petrek@wwt.org.uk
Kane Brides
WWT Conservation Evidence Department
Slimbridge, Glos, GL2 7BT
UK Bretlandi
kane.brides@wwt.org.uk
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