Oil spill response capabilities and technologies for ice-covered Arctic marine waters: A review of recent developments and established practices

Renewed political and commercial interest in the resources of the Arctic, the reduction in the extent and thickness of sea ice, and the recent failings that led to the Deepwater Horizon oil spill, have prompted industry and its regulatory agencies, governments, local communities and NGOs to look at all aspects of Arctic oil spill countermeasures with fresh eyes. This paper provides an overview of present oil spill response capabilities and technologies for ice-covered waters, as well as under potential future conditions driven by a changing climate. Though not an exhaustive review, we provide the key research results for oil spill response from knowledge accumulated over many decades, including significant review papers that have been prepared as well as results from recent laboratory tests, field programmes and modelling work. The three main areas covered by the review are as follows: oil weathering and modelling; oil detection and monitoring; and oil spill response techniques.     

Territorial defence in the great tit (Parus major): Do residents always win?

Summary I removed resident pairs of great tits from their territories for short periods and released them after replacement pairs had occupied the spaces. When two pairs are manipulated in this way into occupying the same territory an escalated contest ensures. Contests between residents and replacements are longer, more likely to involve physical fights and longer fights or displays than contests between established neighbours or residents and intruders. The degree of escalation between residents and replacements is an increasing function of replacement time. It rises to a peak and then diminishes again. The probability that the replacement will defeat the former resident is an increasing function of replacement time, reaching 90% after several days. These results are consistent with the hypothesis that territorial residents win in contests against intruders because of an asymmetry in payoff rather than an asymmetry in resource holding potential or an arbitary convention. A possibly asymmetry in payoff in the great tit is the cost of defending the territory against neighbours. The cost is higher for replacements than for residents.     

Habituation and song repertoires in the great tit

Summary This paper is concerned with the idea that the song repertoires of passerine birds are an evolutionary adaptation to reduce habituation in listeners. In an experiment involving 16 territorial males I played either a single song or a repertoire of songs for 15 two-min trials through a single loudspeaker near the edge of the territory. In a second experiment with 10 birds I played the songs through one of two loudspeakers in different parts of the territory, alternating between loudspeakers on successive trials. The birds tended to habituate more rapidly to single song playback than to repertoires. In the second experiment the overall level of habituation was lower and the difference between the two treatments was less marked.Two features of song repertoire organisation are consistent with the habituation hypothesis (1) the avoidance of low recurrence intervals in switches between song types, and (2) the fact that within repertoire variability is as great or greater than between repertoire varability.The main problem with the habituation hypothesis is that habituation by listeners does not seem to be adaptive, so it is not clear why they should habituate. I suggest a hypothesis. Intruders may assess the density of birds in an area by listening to songs, so that habituation may be a mechanism by which this density assessment is achieved. Repertoires could be a mechanism by which resident birds cheat, through increasing the apparent density of singing birds.     

Optimal foraging and territorial defence in the Great Tit (Parus major)

Summary We describe an experiment designed to investigate the trade-off between foraging and territorial vigilance in the Great Tit. Captive territorial male Great Tits were observed while foraging in a large indoor aviary. They obtained food from two operant patches in which the supply of food was gradually depleted during a visit. We predicted that during control sessions the birds would switch between patches in such a way as to maximise their overall feeding rate. In experimental sessions, we introduced briefly a rival male as an intruder at the start of the test. The foraging male could see the rival only when travelling between patches and not while feeding within patches. We predicted that during experimental sessions birds would switch between patches more often than in control tests, sacrificing food intake for territorial vigilance. Three of the four males tested behaved in approximately the predicted manner. We discuss the use of an inverse optimality argument to provide a calibration of feeding against the benefit resulting from territorial vigilance.     

Learning a time-place pattern of food availability: a comparison between an insectivorous and a granivorous weaver species (Ploceus bicolor and Euplectes hordeaceus)

Summary We compared the ability of an insectivorous weaver bird species, Ploceus bicolor, and a granivorous weaver species, Euplectes hordeaceus to learn time-place patterns of food availability. ln the laboratory both species learned to visit four different feeding places, each at a different fixed time of day. This learned feeding pattern persisted even when every feeding place provided food over the whole day. We found differences in the performance between the two species in phase shift (6 h advance) and blocking (4 h food deprivation) experiments. Unlike the insectivorous species, the granivorous species did not show the learned time-place pattern under these conditions. We suggest that this difference might reflect a difference between the species in the strength of the linkage between time and place. Correspondence to: H. Falk