Vocal individuality has potential for the monitoring of bird species that are otherwise difficult to observe. In this study we assessed the potential of this technique for the monitoring of the globally threatened Corncrake Crex crex based on the analysis of calls recorded in Ireland and Scotland in 1993 and 1994. Discriminant function analysis correctly attributed >80% of individual calls based on five temporal parameters. A high level of individual distinctiveness was also found in the fine temporal structure of calls. When information on fine structure was added to the discriminant function analysis, classification of calls to individuals was improved to 100%. The structure of an individual's call was found to be consistent over the 2‐year period. This study highlighted the problemsassociated with setting criteria for re‐identifying individuals by calls. The consequences of these problems and the potential of vocal individuality for providing monitoring information in this species are discussed.

Male Great Bitterns Botaurus stellaris have individually distinctive boom vocalizations which have been used since 1990 to count the British population accurately. We used vocal individuality to identify birds between years and analyse the survival of the British booming population. We used six instances of Great Bitterns known to be the same birds (from radio tracking and re‐sighting of darvic rings) in successive years to provide a means of identification independent from vocalizations. All of these birds remained in the same territory from one year to the next. Seven spectrogram measures were chosen as quantitative descriptors of Great Bittern booms. Boom similarity was expressed in terms of Euclidean ‘acoustic’ distance between descriptors of pairs of birds. Great Bitterns that were known to be the same birds had more similar booms across years than those known to be different. The acoustic distances and knowledge of site fidelity were used to construct parsimonious rules on which to base re‐identification decisions and to build survival histories. Great Bittern local survival in Britain as a whole was estimated as 70% (± 5.1 se) with survival in north‐west England (at Leighton Moss) higher (82.8%, ± 7.3 se) than that in East Anglian sites (65.2%, ± 5.4 se) (χ12 = 3.4, P = 0.07). Movements of males between years were apparent between sites within the Suffolk and Norfolk coastal regions but not on a large scale. Survival of adult males in East Anglia was positively related to winter rainfall, but there was no significant relationship with winter temperature. There was a positive relationship between the annual population change in East Anglia and the annual local adult survival rate.

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This paper describes the first use of radiotracking to follow closely the secretive Great Bittern Botaurus stellaris , and to quantify its reedbed habitat preferences at a fine scale. Eight males were tracked at two sites in Britain, at which they were mainly resident through the winter. Their median home-range sizes were 14.6, 19.3 and 33.1 ha during the booming, moult and winter periods, respectively, and home-ranges were, on average, composed of 30% open pools and 48% reedbed edge (of 30 m width). Great Bitterns were most often active in reed with 20 cm water depth within the 30-m reed edge next to water, whereas areas of reedbed near scrub or further from the water's edge were avoided. Reed edge adjacent to open pools was preferred over that adjacent to channels and ditches. These results provide a basis for conservation recommendations on the quantity and composition of reedbed habitat and provide the scientific basis for a national programme of reedbed rehabilitation and restoration.

Great Bitterns Botaurus stellaris have experienced a population decline in the UK, such that in 1997 the total number of breeding males was just 11. This study aimed to identify factors affecting productivity, and how management could be used to manipulate this. An intensive study of Great Bittern breeding success was conducted between 1997 and 2001. The date that males established their booming territories was closely correlated with when females started nesting. Wetter sites with greater fish densities had males that established their booming territories earlier in the season. However, only the date that males started booming determined when females started nesting. The mean clutch size of Great Bitterns was four and the only cause of nest failure was predation. Of eight nests suspected to be second attempts the mean interval between these first and second attempts was 12.25 ± 0.88 (sd) days (range 8–15). The fate of radiotagged chicks followed to fledging revealed that the overall probability of a chick surviving to fledge was 39.1%. Daily losses of Great Bittern chicks due to starvation/exposure accounted for 76.25% and predation 21.25%. The youngest chicks in poor condition were most likely to die, particularly in periods of high rainfall. A simulated renesting model allowed estimation of Great Bittern productivity as 1.24 chicks per female and 1.52 nesting attempts per female. Habitat management, or lack of water control that resulted in sites being drier in spring, delayed nesting, although statistically there was no difference in productivity compared with wetter sites.