Diurnal activity patterns suggest nocturnal foraging in Northern Fulmar (Fulmarus glacialis) / Dagligt virksemi hjá havhesti (Fulmarus glacialis) bendir á, at hann leitar sær føði um náttina

Jóhannis Danielsen

Abstract


Úrtak

Eygleiðingar við myndatólum av í alt 12 havhestareiðrum í Føroyum árini 2006 (sjey reiður) og 2007 (fimm reiður) vístu, at greiður samanhangur var millum, nær havhesturin kom til og fór av reiðrinum, og daglongd, sólarris og sólsetur. Við tveimum undantøkum vórðu øll skiftini á reiðrinum gjørd millum kl. 7 um morgunin og kl. 19 um kvøldið. Ungarnir  vórðu  sum  oftast  mataðir  millum  kl. 9 um morgunin og kl. 18 um kvøldið. Hesar eygleiðingar saman við úrslitunum frá eini føðikanning, ið vísti týdningin av prikkafiski sum føði, geva góða ábending um, at havhesturin leitar sær føði um náttina.

 

Abstract

The continued camera observations of nest­site attendance at a total of 12 nests in 2006 (7 nests) and 2007 (5 nests) showed a strong correlation between nest­site attendance and sunrise, day patterns. Optical devices for night observations have been available for a long time but have rarely been used to study nest­site attendance by this species.

     I studied the daily nest­site attendance, chick feeding schedule and incubation rhythm of the Northern Fulmar at a small colony on the Faroe Islands throughout night and day for two years using surveillance cameras with infrared LEDs. The attendance patterns were analysed to see if they correlated to sunrise, sunset and day length and analysed in relation to time of day for incubation shifts, and feeding of the chicks. Since a previous study showed that the diurnally migrating Glacier lantern fish (Benthosema glaciale) was an important part of the diet of the Northern Fulmars on the Faroe Islands (Danielsen et al., 2010), I postulate that the birds would be away from the colony at night, in order to forage out at sea.

     Furthermore underlining the importance of doing observations during both day and night is the fact that although birds might show signs of breeding by staying faithfully at the nest and apparently incubate during day­time, this is not necessarily true when also adding observations during the night. This can easily lead to biased estimates regarding how many of the birds in the colony are actually producing eggs. This information is important for e.g. estimating breeding colony size (Mallory and Forbes, 2007).

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DOI: http://dx.doi.org/10.18602/fsj.v59i0.48

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