Náttúrufræðingurinn - 1965, Síða 19

NÁTTÚRUFRÆÐINGURINN
to September o£ the same year several wood pigeons were seen at Svínafell. On
September 15 tcn birds were counted, six of these being immatures, while three
or four were adults. Wood pigeons may therefore have nested successfully at
Svínafell in the summer of 1963, although concretc proof is lacking. In 1964 wood
pigeons were first observed on April 4, when one bird was seen at Svínafell.
During the sunnner of 1964 wood pigeons were frequently seen near the farm,
up to six being seen at one tirne. On July 31, 1964 a wood pigeon’s nest was
discovered on a ledge in a narrow gorge on the mountain slope above the farm
(fig. 1). The nest contained a newly hatched young that had Iteen dead for a
considerable time, and an egg containing a dead but fully developed embryo.
The nest (fig. 2) was composed of small birch sticks and was completely con-
cealed by a rank growth of angelica. Water from the clilfs above constantly
dribbled into the nest, although it had not heen raining lor tlie last few days.
Tliis probably explains why breeding failecl. öne adult bird was seen sitting
in a birch tre just above the nest. This tree had obviously been mucli frequented
by the pigeons, since parts of it were stained white by their excrements. The
nest was visited again on August 2, 1964, when one pigeon was again found sit-
ting in the tree.
This constitutes the first substantiated nesting record of the wood pigeon in
Iceland.
Örnólfur Thorlacius:
Hei 1 adingul linn
I.íkamar manna og dýra styðjast cinkum við tvær aðferðir til að
samstilla störf líffæranna. Annars vegar eru taugaboð, sem berast
eftir lastmörkuðum brautum tauganna, hratt og örugglega. Hins
vegar eru hormónaboð. Hormón eða vakar eru elni, sem myndast
víða um líkamann og dreifast með æðum frá myndunarstaðnum.
Hvert hormón hefur einitver skilaboð að flytja, stundum aðeins á
einn stað eða til einnar gerðar líffæra, en sum hormón hafa áhrif
víða um líkamann. Hormónaboð berast hægar en taugaboð, hins
vegar endast hormónin nokkra hríð í blóðinu.
Allmörg líffæri gegna því starfi einu að framleiða hormón, Svo
sem heiladingull, skjaldkirtill og nýrnahettur. Nefnast þessir kirtlar
innkirtlar, vakakirtlar eða lokaðir kirtlar til aðgreiningar frá út-
kirtlum eða opnum kirtlum, sem opnast um rásir út á ytra eða innra