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Socotra Cormorant Phalacrocorax nigrogularis

Socotra
C
ormorants
page 2 of 5

My first encounter with the cormorants on Hawar in November 1994 was a turning point in my life, it was a moment I shall never forget, and although I have now visited them hundred of times they never cease to amaze me. The more I watch, the more I realize just how little I actually know about their breeding biology. In 2003 I followed them on an almost daily basis from June through to October and was able to document some aspects of their communal behaviour outside of the breeding season. It was always my intention to do the same for the balance of the year particularly during the actual breeding season however circumstances always contrived to break the routine and I have never been able to achieve this goal. I have watched in short bursts at various times while they are breeding and noted some remarkable behaviour however I have often never been able to re-observe the same aspects in the following seasons. One such aspect was the occurrence of cannibalism involving the juveniles. In December 2003 I witnessed over the course of a week or so several incidences of juveniles scavenging for dead chicks and then eating them whole. In fact I even observed juveniles fighting over a carcass on numerous occasions.

The predatory large attendant gulls around the colony steal thousands of eggs, and eat large numbers of chicks during the course of a season. The smallest chicks are often swallowed whole as are the eggs, larger chicks have their guts torn out which are then eaten and the balance discarded. (Just how many chicks gulls take in a season is another fact I have been trying to estimate.) The gulls besides scavenging anything they can get their beaks on, harass or mob a sitting bird, hoping to force it eventually off the nest,
those nesting around the edge of the colony are the most vulnerable. Experienced breeders sit tight and fight back often with the assistance of sitting birds on neighbouring nests who peck at anything that comes within extended neck range.  When a raid is successful often more than one sitting bird would flee exposing several nests and their contents to predation by the gulls. The gulls instantly mob any exposed nests fighting over both eggs or chicks, booty is more often carried off to be eaten elsewhere. Eggs and live chicks are regularily dropped from a height, before being eaten, their scattered remains litter the surrounding area.

Were the juvenile cormorants mimicking the gulls, was it normal behaviour or a question of simple survival? insufficient food being supplied? were the chicks orphaned? I can only guess. However on one occasion while I watched the colony from fairly close range I was taken by surprise when a nearly fully fledged juvenile (see photos) approached the nest immediately in front of me (less than 10 feet away) moved in on the sitting bird which, after some preliminary pecking and neck movements allowed the juvenile to occupy the nest. The adult sitting bird then wandered away, took off and went for a bathe. In the meantime the juvenile had stood up and was hovering over the single chick in the nest, instinctively the chick raised its head in anticipation of being fed, the hovering juvenile, lowered its head, opened its beak in a mock feeding posture encouraging the chick to attempt to obtain food by sticking its head up into its throat. Rather than being fed the chick received a sudden and violent pecking about the neck, the juvenile by this time had the chick suspended from its beak by the neck, and proceeded to pickup, drop and peck the chick until it was near dead at which point it then tried to position the chick now on the ground in its beak ready to be swallowed. What the juvenile didn't expect at this moment was that another juvenile of about the same age that had been watching from close by suddenly decided that this chick was his, it promptly grabbed what was probably by now a dead chick and after a long tussle and attempts by the other to reclaim the chick disappeared to another part of the colony with the chick firmly clasped in its beak. When it felt safe from disturbance from the first bird which had followed him part way the chick was in a single motion swung up and swallowed head first. I was able to photograph some of the key moments of the tussle but unfortunately the film ran out, I have placed the images scanned from the prints in the accompanying photo album. Prior to that point using the camera never crossed my mind. This was the only time I observed a juvenile cormorant actually contrive to kill then eat a chick, throughout that period of observation I observed a total of seven scavenged carcasses being eaten.