The status of the Corncrake Crex crex in Britain in 1998

A census of Corncrakes throughout Britain was carried out in 1998. National Grid squares of 10 km in the Hebrides, Northern Isles and the mainland of Highland Scotland known to have held the species during the breeding season since 1988 were searched systematically by night for singing males. A sample of such squares elsewhere in Scotland was also searched. In addition, bird-watchers and the general public were encouraged by press publicity to contribute records of singing birds, which were checked for accuracy. A total of 589 singing males was counted in 93 10-km squares. Ninety percent of the population was in the Hebridean Islands. The total count was 23% larger than in the previous census in 1993 and 3% larger than in 1988. All surveys of distribution and censuses between the late 19th century and 1993 recorded a progressive decline in the national population and range. The average rate of population decline between 1988 and 1993 was 3.5% per year, but between 1993 and 1998 the population increased by an average of 4.2% per year. However, annual counts from 1993 to 1998 in core areas that held more than 90% of the population, showed that this overall increase resulted from four successive annual increases of 4–16% followed by a decline of 15% between 1997 and 1998. There was considerable variation among islands and areas in the rate of change of their Corncrake numbers.     

The increase in the Corncrake Crex crex population of the United Kingdom has slowed

Capsule The UK Corncrake population increase has slowed, but has rapidly recovered from a large decline in 2013.

Aims To provide an update on the population size and distribution of breeding Corncrakes in the UK, including the results of the most recent full national survey and annual monitoring of the core population.

Methods A full survey of singing Corncrakes was undertaken in the UK and the Isle of Man in 2009, following the last full censuses in 1978/79, 1988, 1993, 1998 and 2003. Monitoring of singing male Corncrakes within the core range in northern and western Scotland has been undertaken annually since 1993.

Results The 2009 results show that numbers increased substantially since 2003, from 829 to 1166 singing males. Corncrake numbers in the core range have increased in 17 of the 21 years between 1993 and 2014, and peaked at 1274 singing males, in 2014. Numbers of singing males dropped by 24% between 2012 and 2013, probably due to a particularly cold spring in 2013 that inhibited growth of vegetation cover, but numbers recovered markedly in 2014.

Conclusion The recovery of the UK Corncrake population has continued since a low point in 1993. However there are no signs of range expansion into mainland UK, away from the core breeding areas in Scotland. The large decline in the core population between 2012 and 2013 highlights the sensitivity of the population to external factors, although the subsequent increase in 2014 shows a capacity for rapid recovery.     

Effects of weather on the survival and growth of Corncrake Crex crex chicks

Weather conditions during the early life of precocial chicks of some bird species have marked effects on survival and may also cause changes in adult population size. In this paper, we use data from broods with radiotagged mothers to examine correlations of growth rates and survival of Corncrake Crex crex chicks in Scotland and Ireland with temperature and rainfall. The loss of whole broods before they reached independence was infrequent and not correlated with temperature or rainfall. Loss of some chicks from broods before independence usually occurred and multiple regression analysis indicated that the proportion of chicks that survived increased with decreasing initial brood size, increasing temperature and decreasing rainfall. However, the magnitude of the effects of weather on survival were quite small. The rate of weight gain of chicks varied considerably within and among broods. The mean daily weight gain rate of broods decreased significantly with increasing rainfall, and variation in the weight of chicks within broods was greater for broods whose mean rate of weight gain was low.     

Timing of autumn migration of young Corncrakes Crex crex

Knowledge of the timing of migration of young Corncrakes is required for effective implementation of conservation measures. Forty Corncrake chicks were radiotracked during the period between independence and departure from the natal area to determine the age and time at which fledged juveniles depart on migration. Departure occurred between early August and mid‐September at a mean age of 44 days, around the age at which growth of the primary feathers ceases. Chicks from later broods are exposed to greater risk of being killed during mowing, but provision of late mowing options in conservation schemes could enhance their survival.     

Macrogeographic variation in the call of the corncrake Crex crex

This study was conducted to characterise macrogeographic variation in the vocalisation of the corncrake Crex crex, a bird species with a non‐learned and highly stereotyped call. We also examined: 1) whether call characteristics remained stable across successive breeding seasons within two of the study populations and 2) whether call similarity was related to distance between populations. Recordings of 352 males from eight populations were analysed. The analyses focused on variation in 1) temporal characteristics (duration of syllables and intervals, duration of the intervals between consecutive maximal amplitude peaks within syllables, called pulse‐to‐pulse duration (PPD)), and 2) spectral characteristics (minimal and maximal frequency, frequencies below which 25%, 50% and 75% acoustic energy of signal is distributed). We found significant differences in most of the temporal and all of the spectral characteristics between populations. No differences were found in PPD. Significant interannual differences in spectral characteristics were found in both of the populations examined, whereas differences in temporal characteristics were only observed in one population. In general, geographic variation in calls showed clinal distance‐dependence, where distant populations showed larger differences in call than neighbouring populations. Our results show that geographic variation in corncrake calls may be very dynamic in the short term and that within‐population variation may occur on the same scale as between‐population variation. This finding is surprising because call characteristics in non‐learners are essentially inherited, and genetic transmission should be very slow. We suggest that the social interactions between males and/or the specific dispersal patterns of this species and the low site fidelity of adult and young birds may be responsible for such pattern.     

长脚秧鸡重新在新疆发现

长脚秧鸡 (Ｃｒｅｘｃｒｅｘ)属于鹤形目秧鸡科长脚秧鸡属 ,是国内唯一在新疆有分布的珍稀候鸟 (旅鸟或繁殖鸟 )。最初由Ｌｕｄｌｏｗ等 ( 1934)报道了该种在中国新疆和西藏的分布。之后的半个多世纪 ,国内一直无人记录或采集到标本。各种论著均沿袭和引用Ｌｕｄｌｏｗ等的原始报告 ,乃至所有的文献记录都大同小异。该种已被列为濒危物种 ,纳入 1989年版的中国国家重点保护名录 (Ⅱ级 ) ,同时也被国际鸟盟(ＢｉｒｄＬｉｆｅＩｎｔｅｒｎａｔｉｏｎａｌ)纳入 1998年公布的世界濒危鸟种名单。1998年 5～ 6月和 1999年 6～ 7月笔者多次在新疆伊…     

The introduction of subsidies for grassland conservation in the Italian Alps coincided with population decline in a threatened grassland species,the Corncrake Crex crex

Capsule We analysed Corncrake population trends between 1997 and 2012 and evaluated changes before and after the introduction of subsidies for grassland conservation in 2000, which indirectly promoted unfavourable mowing practices over most grasslands in Trento province. According to both early and late season counts, the species has significantly declined in the study area since the early 2000s. Agri-environmental subsidies that are not adapted to the ecological requirements of the species may fail to achieve conservation objectives.     

A new method for estimating the adult survival rate of the Corncrake Crex crex and comparison with estimates from ring-recovery and ring-recapture data

The mean annual survival rate of adult Corncrakes Crex crex was estimated by three independent approaches: ring-recovery, ring-recapture and the shape of secondary remiges. The last method is new and uses measurements of the shape of the tips of the secondaries, which changes in the first post-juvenile wing moult to become less pointed. The estimates obtained by the three approaches were mutually compatible and indicated that annual survival is likely to be within the range 0.2–0.3. This low survival rate is likely to make the growth rate of Corncrake populations particularly sensitive to the effects of agricultural and conservation management on breeding success and recruitment. The survival rate of adult female Corncrakes was estimated for the first time (0.259) and was found not to differ significantly from an estimate for adult males (0.298) made in the same study area by the same method. It is concluded that the method based upon population counts and measurements of the shape of remiges has potential value for studies of the demography of Corncrakes and other species.     

Female Corncrake(Crex crex) singing in the wild

Summary The male Corncrake (Crex crex) has a characteristic mating call. In aviary it has been shown that females can also produce a call similar to the male's typical crex crex. I describe a strikingly different call produced by a female on Öland, southeast Sweden. The sex identification was based on the small size during close examination in the hand. The female call has a similar rhythm to the male call but lacks the rasping of the male and is almost a barking sound. The female was heard calling continuously at night throughout a three-week-period. Another bird producing the same call was heard about 100 m from the caught female suggesting two females in the same field. No male Corncrakes were heard in the field during the period when the female was calling. Possible explanations for this behaviour and the function of the call is discussed.

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Rufe eines weiblichen Wachtelkönigs(Crex crex) im Freiland

Zusammenfassung Männliche Wachtelkönige (Crex crex) haben charakteristische Balzrufe. In Gefangenschaft gehaltene weibliche Wachtelkönige rufen ebenfalls männchenähnlich crex crex. Dieser Artikel beschreibt einen bisher unbekannten Ruf eines weiblichen Wachtelkönigs von der Insel Öland/SE Schweden. Die Geschlechtsbestimmung erfolgte aufgrund der geringen Maße. Die Rufe des Weibchens zeigten einen ähnlichen Rhythmus wie die der Männchen, ihnen fehlt jedoch der knarrende Klang und sie klingen eher bellend. Das rufende Weibchen wurde über drei Wochen regelmäßig nachts gehört. Ein weiterer Vogel mit den gleichen Rufen wurde etwa 100 Meter neben dem gefangenen Weibchen gehört, was darauf deutet, daß es sich um zwei Weibchen in dem gleichen Feld gehandelt hat. Rufende Männchen wurden während dieser Zeit nicht gehört. Die Bedeutung dieser Weibchen-Rufe wird diskutiert.

     

Management of cover areas may increase numbers of breeding Corncrakes Crex crex

Capsule Density of Corncrakes is greater in areas of positively managed non‐crop cover vegetation which occur alongside fields managed to enhance breeding success.     

Acoustic location of conspecifics in a nocturnal bird: the corncrake Crex crex

Although the use of sounds in spatial orientation is widespread among animals, only a few groups advanced such specific adaptations as echolocation. In contrast, practically all animals and night-active species in particular, must occasionally orient themselves relative to invisible but audible objects such as a hidden rival or predator. In this study, I would like to determine the impact of locating which involves the use of acoustic parameters of sender’s vocalisations by receivers and changes of positions and triangulation of sender’s vocalisations by receivers in estimating the distance to the sender during night-time territorial interactions of the corncrake (Crex crex). Males were subjected to two kinds of stimuli: approaching one, imitating the change of the distance of the calling intruder toward the focal male while keeping the direction constant, or stationary stimuli, involving acoustic stimulation with no motion. Although males subjected to approaching stimulation moved longer distances, in both stimuli groups, males moved predominantly toward or out of the playback speaker, and only occasionally made sideway movements. However, the results gave no evidence of corncrakes moving specifically in order to locate the source of the sound; they suggest that males moved toward or away from the already located sound. The fact that males moved longer distances in response to approaching than stationary stimuli indicates that they were able to perceive the change of the distance to the playback speaker based only on structural parameters or amplitude of the calls played.     

Male Corncrakes Crex crex extend their home ranges by visiting the territories of neighbouring males

Capsule Radiotracked male Corncrake often intruded on the territories of neighbouring males.

Aims To test that intruders' visits are goal-directed, not just a by-product of extended spatial activity during daylight hours.

Methods Using radiotelemetry, we sampled a total of 20 three-day home ranges from 11 tagged males. We recorded daily vocal activity and used a permutation test to see if the movements of tracked males were independent of the position of neighbouring males.

Results The majority of males who had a neighbouring male, up to approximately 600 m from their night calling site, undertook goal-directed visits to the neighbour's territory. Males undertook these visits every day, or every other day, when the neighbours were close. Males undertook visits approximately once every three days when they were more distant. The time spent in the neighbour's territory was longest where the distance between night calling sites was about 200 m. Males tended to be silent in neighbour's territory, apparently to prevent confrontation. Otherwise the distance of neighbouring males did not significantly affect daytime vocal activity. Visiting males tended to sing more often in their home territories.

Conclusions Daily movement of the majority of males was towards the neighbouring male's calling site. We suggest that the purpose of these visits was to seek females. These males may try to drive a female into their territory or gain extra-pair copulation.     

Habitat preference of female Corncrakes Crex crex: implications for the conservation of breeding sites in a secretive species

Capsule: Forb-rich and diverse, annually mown vegetation is the preferred Corncrake Crex crex breeding habitat in floodplains.

Aims: To identify habitat preferences of female Corncrakes and characteristics of breeding sites in floodplain habitats and derive recommendations for management.

Methods: We tracked six female Corncrakes and compared vegetation characteristics at 78 male calling sites with regard to breeding records and diurnal call activity of males, because we expect the latter to indicate female occurrence. Additionally, we analysed how practice and timing of land use in the preceding year affected vegetation structure.

Results: Females preferred areas with high cover of forbs and a distinct relief heterogeneity, which was associated with overall vegetation diversity. All calling sites with breeding records and diurnal call incidence of males showed high forb and low sedge cover, low litter heights and a close location to ditches. Favourable conditions were best provided by mowing in the preceding year.

Conclusion: In eutrophic habitats, female Corncrakes preferred a vegetation structure created by annual mowing. Because nests and unfledged chicks are threatened by mowing operations, we recommend an alternating management regime based on the identification of breeding sites using male diurnal calling activity.     

Functionally similar acoustic signals in the corncrake (Crex crex) transmit information about different states of the sender during aggressive interactions

We combined playback experiments with hormonal manipulations to study the information content of acoustic signals during aggressive interactions between male corncrakes. During territorial conflicts, fights are uncommon, but the intensity of signaling usually increases. Such signals can be temporally and contextually associated with many aggressive behaviors and most likely function as threats or as indicators of the sender's quality or motivation. However, such correlational data are unsatisfactory for the proper interpretation of the function and information content of signals. Experimental tests are required to determine whether signals and aggressive behaviors are controlled by common or independent mechanisms. In our experiment, we assigned subjects to four groups: testosterone-implanted birds, flutamide-implanted birds, birds with empty implants, and non-captured control birds. Males produced two types of calls (quiet soft calls and loud broadcast calls), both of which are known to be reliable predictors of aggressive escalation. When testosterone action was blocked with flutamide, males significantly limited the amount of time spent close to the playback speaker and stopped responding to playback with soft calls. Broadcast calling was unaffected by the blockage of testosterone. Conversely, increased levels of testosterone neither affected calling nor the time spent near the speaker, indicating a permissive, rather than a graded effect of androgens. We concluded that, despite the seemingly similar function, both signals may transmit information about different states of the sender; soft calls seem to imply a threat of force, while broadcast calls appear to be more similar to an announcement, which is only indirectly associated with a male's aggressive behavior.     

Use of microsatellite‐based paternity assignment to establish where Corn Crake Crex crex chicks are at risk from mechanized mowing

We used microsatellite DNA to assign probable parentage of young Corn Crakes to adult males and females and used these assignments to estimate the distribution of distances between broods of chicks and juveniles and the night‐time singing place of the father at the time of initiation of the clutch. Estimated distances for broods of young chicks were in accord with those estimated previously by radiotracking, but distances were greater for older unfledged independent chicks not studied previously. Our results indicate that modifications of the timing and method of mowing to reduce losses of nests and chicks should be implemented inside an area within about 500 m of the singing places of male Corn Crakes, rather than the 250 m previously considered to be safe.