Observations of Northern Fulmar
Fulmarus glacialis behaviour while at sea
Dr Russell B Wynn
Southampton Oceanography Centre
Observations of Northern Fulmar Fulmarus glacialis at sea north of Shetland during summer 2002 revealed an interesting variety of behaviour, generally involving birds feeding or loafing around the ship. Several individuals were seen preying upon jellyfish, which were located and eaten by birds swimming on the sea surface. In addition, defensive postures in response to Great Skua Catharacta skua attacks were seen to be 100% successful, whereas other species nearby such as Sooty Shearwaters Puffinus griseus and Northern Gannets Morus bassanus were relatively defenceless against such attacks. Great Skuas were never seen approaching closer than about one metre to feeding Northern Fulmars; this distance is roughly equivalent to the ‘spitting’ range of the Fulmar, suggesting that individual skuas either had previous experience of this defence or they have inherent knowledge of its potential danger. Finally, Northern Fulmars were frequently observed pecking at the tails of Northern Gannets sitting on the water. The reasons for this latter behaviour are unclear.
This brief note describes a series of interesting observations, with accompanying photos, relating to behaviour of Northern Fulmars Fulmarus glacialis during a scientific research cruise on the R/V Kommandor Jack from July 26th to August 21st, 2002. The study area was at sea between 100 and 300 km north of Shetland, and observations were made in a variety of weather conditions. A summary of all cruise sightings can be found in Wynn (2003) or on this webpage.
The first observation relates to feeding behaviour. On several occasions both light-morph and dark-morph Northern Fulmars sitting on the sea around the ship were seen to feed on live jellyfish at the surface (Figs 1 and 2). Both Common Jellyfish Aurelia aurita and Lion’s Mane Jellyfish Cyanea capillata were taken. The Northern Fulmars ate the jellyfish by pulling and tearing at the soft tissue of the dome, using their feet as paddles to obtain leverage (Fig. 2). This method ensured that the Northern Fulmars avoided any contact with the underlying stinging tentacles. The feeding behaviour appeared to be opportunistic, as it was only observed in birds loafing around the stationary ship in relatively calm conditions. It seems likely that jellyfish are probably harder to locate in rougher sea conditions. Previous studies have recorded Northern Fulmars eating jellyfish (and other small organisms associated with the jellyfish) in deep offshore waters (Fisher, 1952; Harrison, 1984; Camphuysen and Franeker, 1996; Camphuysen, 1996). Of interest, Hume and Pearson (1993) mention that Northern Fulmars have also been recorded eating floating rubber contraceptives discarded with sewage, presumably mistaking them for jellyfish.
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Figure 1: Dark-morph Northern Fulmar Fulmarus glacialis approaching a Common Jellyfish Aurelia aurita in the water. |
Figure 2: Light-morph Northern Fulmar Fulmarus glacialis eating Common Jellyfish Aurelia aurita. |
The second observation relates to defensive behaviour. When waste food was discarded from the ship it was immediately seized upon by feeding Northern Fulmars (Fig. 3), often closely shadowed by prowling Great Skuas Catharacta skua. However, as soon as a Great Skua approached too close to one of the feeding Northern Fulmars, the targeted bird would respond by adopting a defensive posture with 1) raised wings and tail 2) the head slightly tilted back and 3) the beak facing upwards and outwards (Fig 4). This posture is commonly displayed by adult and young birds when under threat at their onshore breeding sites, and is described in Fisher (1952). The head and beak (and the accompanying threat of ejected oil) would always face the incoming skua, preventing them from landing on or circling behind the Northern Fulmar. In fact, at no time were Great Skuas seen coming closer than about one metre from feeding Northern Fulmars (Fig. 4), presumably because this would bring them within ‘spitting’ range, which is quoted at about 1-1.5 m by Fisher (1952). During this study, the defensive posture was always 100% successful in deterring Great Skuas, and they were never seen to take food from any Northern Fulmar (although note that some other studies have shown Great Skuas occasionally bullying food from Northern Fulmars, e.g. Furness (1987), who states that Great Skua attacks on Northern Fulmars have been regularly recorded in Iceland, although they are highly localised and apparently only carried out by a small number of individuals.). The general success of the Northern Fulmars’ defence suggests that 1) every skua deterred in this way has had first-hand experience of being ‘spat at’ or has observed other skuas receiving such treatment, or 2) the skua holds inherent knowledge and is aware of the damage regurgitated oil can inflict upon their feathers (leading to inhibition of flight, insulation and waterproofing). It is interesting to note that during this study regular observations were made of Great Skuas successfully stealing regurgitated food items from other seabirds nearby that lacked such defences, including Sooty Shearwaters Puffinus griseus, Northern Gannets Morus bassanus (Fig. 5) and Black-legged Kittiwakes Rissa tridactyla. On occasions, Sooty Shearwaters were noted ‘plunge-diving’ in their efforts to escape from the skuas.
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Figure 3: The 'resident' flock of Northern Fulmars Fulmarus glacialis around the ship immediately after waste food was thrown overboard. |
Figure 4 (a and b): Examples of defensive posture of Northern Fulmars Fulmarus glacialis in response to close approach by Great Skuas Catharacta skua. Note the distance between the birds is about one metre, roughly equivalent to the spitting range of the Northern Fulmars. |
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The third observation relates to an example of unusual, and as yet unexplained, behaviour. On several occasions Northern Fulmars were seen to swim up behind unsuspecting Northern Gannets and give their tail feathers a sharp tug with their beak, although at no time were feathers actually removed. Sometimes up to three Northern Fulmars could be seen doggedly pursuing an unfortunate Northern Gannet through the water. The Northern Gannets were predictably hostile towards this behaviour, and would often turn and peck at the Northern Fulmars. However, they were never seen to inflict any damage upon their tormentors. There appeared to be no obvious reason for this behaviour, but the fact that it mostly occurred when the birds were loafing around the ship before or after waste food was thrown overboard (Fig. 3) raises the possibility that the Northern Fulmars were actually acting aggressively towards the Northern Gannets.
In summary, these observations highlight the adaptability and durability of Northern Fulmars while at sea, and provide some insights as to why they are able to dominate even their most aggressive rivals in mixed feeding groups. |
Figure 5: Great Skua Catharacta skua pirating food from a Northern Gannet Morus bassanus. |
References
Camphuysen C.J. 1998. De Kwalvlo Hyperia galba als vogelvoedsel. Het Zeepaard 58(6): 163-166.
Camphuysen C.J. & Franeker J.A. van 1996. Jellyfish and fishery waste as food sources of Northern Fulmars Fulmarus glacialis feeding around St Kilda. Sula 10(4): 143-150.
Fisher, J. 1952. The Fulmar. Collins, London, 496pp.
Furness, R.W. 1987. The Skuas. T & A.D. Poyser, Calton, 363pp.
Harrison N.M. 1984. Predation on jellyfish and their associates by seabirds. Limnol. Oceanogr. 29(6): 1335-1337.
Hume, R. & Pearson, B. 1993. Seabirds. Hamlyn, Hong Kong, 160pp.
Wynn, R.B. 2003. North of Shetland. Birdwatch 127: 25-27.
