Mute swan (Cygnus olor) winter distribution and numerical trends over a 16-year period (1987/1988–2002/2003) in France

The numbers of mute swans (Cygnus olor) at 98 wetland locations in France were monitored monthly during the winter (December–February) for 16 years by a national network of observers as part of a broader national wildfowl monitoring scheme. Log-linear Poisson regressions with TRIM software were used to estimate missing counts and produce national numbers and indices. These corrected indices were in turn used to calculate an average annual rate of change and the associated confidence interval that subsequently enabled the computation of a cumulated (global) rate of change and associated confidence interval. The latter were interpreted to classify the numerical trends over the whole period. For the six wetlands with the largest numbers of mute swans, average numbers of swans were also compared between wetlands and months. General Linear Models were then used to test simultaneously for (1) differences between years and between wetlands for each month and (2) between years and between months separately for each of the six wetlands. The mute swan average annual rate of change was >7% for each month. The global rate of variation corresponded to a “strong increase” after TRIM analyses. This result strongly supports the necessity of maintaining both national and international monitoring schemes in order to be able to quickly detect major increases in swan numbers at specific sites, particularly where increasing numbers may result in a conflict with farmers or in inter-specific competition with other waterbirds and/or represent a possible sanitary/public health hazard due to the potential for swans to carry avian influenza viruses.     

Patterns of plasma progesterone, androgen and oestrogen concentrations and in-vitro ovarian steroidogenesis during embryonic diapause and implantation in the mink (Mustela vison)

Peripheral plasma progesterone concentrations exhibited an increase 10 days before implantation, coinciding with the resumption of blastocyst growth and with a decrease in plasma androgen values (DHA, androstenedione, testosterone). No definite pattern of oestrone was observed and oestradiol concentrations remained undetectable. The production of steroids by dispersed luteal cells showed that the growth of the corpora lutea paralleled that of blastocysts and resulted in hypertrophy followed by hyperplasia of the luteal cell. The production of progesterone in the medium increased with blastocyst size up to implantation; it was enhanced by mink charcoal-treated serum, but prolactin, LH, FSH or a combination of these hormones did not affect the progesterone production, whatever the stage of diapause. DHA and androstenedione secretion increased in the two last stages of blastocyst growth and was enhanced by LH. The conversion of androstenedione and testosterone into oestrone and oestradiol was observed at all stages of embryonic diapause, indicating that corpora lutea contain aromatase activity even at an early stage. The secretion of oestrone was higher than that of oestradiol. The non-luteal tissue contributed up to 50% of the steroid production; while progesterone and androgen production remained constant, that of oestradiol decreased at the end of the delay period. These results indicated a change in the size and the secretory capacity of the luteal cell related to blastocyst development and implantation. Although progesterone was the main product of the corpora lutea, androgens and oestrogens were also secreted.     

Climatic conditions during migration affect population size and arrival dates in an Afro-Palaearctic migrant

Long-distance migrants are particularly susceptible to climate change because of their multi-stage life-cycle, but understanding how climatic conditions at each of these stages influence population dynamics remains a key challenge. Here, we use long-term data from a UK population of Sand Martins Riparia riparia, a declining Afro-Palaearctic migrant, to investigate how weather on the wintering grounds and at passage sites impacts population size and arrival date. General linear models revealed that population size increased and arrival date advanced over the study period, and both were predicted by regional climatic variables in the previous winter and on passage. These results add to a growing body of evidence showing that population change in migrant birds is influenced by climatic conditions at all stages of the life cycle.     

Effect of ovariectomy at two periods of the year on LH and FSH basal concentrations and pituitary response to LHRH in the brown hare (Lepus europaeus)

In the brown hare, fertile mating takes place from the beginning of December to September. Seasonal variations of basal concentrations of LH and FSH, and pituitary response to a monthly i.v. injection of LHRH were studied in intact control females and in females ovariectomized during the seasonal anoestrus (OVX1) or during the breeding season (OVX2). In intact females, both basal and LHRH-stimulated LH levels showed an annual variation, with minimal values during anoestrus. During the breeding season, the LH response to LHRH exhibited a biphasic pattern. In contrast, there was no clear seasonal variation in basal and LHRH-stimulated FSH concentrations. After ovariectomy during anoestrus, basal LH remained low for 2 months and began to increase in December. After ovariectomy during the breeding season, LH basal concentrations increased within a few days after the operation. Thereafter, LH values remained high in both groups of females until September, and decreased significantly as in intact females. The pattern of LH release after LHRH remained monophasic in the two groups of ovariectomized females. In OVX1 females, the LH response increased as early as October, was maximum from December to April and decreased progressively until October. IN OVX2 females, the LH response decreased regularly after ovariectomy to a minimum in October. In the 2 groups of ovariectomized females, basal FSH concentrations and pituitary response to LHRH rose rapidly after ovariectomy and did not vary significantly thereafter. These results showed a direct central effect of season on the regulation of basal concentrations of LH, modulated by a negative feed-back of ovarian secretions during the breeding season. In intact hares, the enhanced LH response after LHRH during the breeding season was related to an acute positive effect of ovarian secretions. The regulation of FSH was less dependent on season and remained under a negative control of the ovary throughout the year.     

The effects of geolocators on return rates,condition, and breeding success in Common Sandpipers Actitis hypoleucos

ABSTRACT

Capsule: Fitting geolocators to Common Sandpipers Actitis hypoleucos did not affect their return rates, return dates, body condition or reproductive success, but did cause leg injuries in some individuals.

Aims: To investigate the effect of fitting geolocators to Common Sandpipers on their return rates and timing, the condition in which they return and their subsequent breeding success.

Methods: We fitted geolocators to colour-ringed Common Sandpipers and monitored them throughout the breeding seasons prior to migration and following return from their wintering grounds. We then compared return rate, return date, change in body condition, hatching success, and fledging success between birds with and without the tags. We also fitted a number of smaller geolocators to wintering individuals in Africa and compared their return rates with a control group.

Results: We found no significant differences between birds with and without geolocators in any of the variables measured. However, several individuals fitted with the larger tags were found to have incurred leg injuries.

Conclusion: Our study highlights the need for complete transparency when reporting the effects of geolocators and shows the importance of continuous monitoring of individuals when carrying out tracking studies.     

Ovarian and Testicular Function in the Blue Fox (Alopex Lagopus) after Oral Administration of Fenchlorphos During the Breeding Season

The possible effect of fenchlorphos, 0-0-dimethy1-0-(2.4.5-trichlorophenyl) phosphorothioate, upon the reproductive endocrinology in blue foxes (Alopex lagopus) was investigated. Five females were administered fenchlorphos orally at a dose of 100 mg/kg daily from 10 days before oestrus and up to the 21st day of gestation. This dose represents the therapeutic dose for the treatment of sarcoptic mange. Blood samples were collected for the analyses of progesterone, oestradiol-17β and luteinizing hormone (LH) in plasma. The vixens were ovario-hysterectomized on day 23, except 1 animal in the control group which was operated on day 17. Additionally, sperm quality and mating performance in 3 male blue foxes, which were administered 100 mg/kg fenchlorphos daily during the first 3 weeks of the mating season, were examined. Pregnancy was recorded in 2 medicated and 4 control animals. No pathological changes were observed in the uterus and the ovaries. The plasma concentrations of the hormones were similar to those obtained from the control group. No evidence of any disturbances concerning spermatogenesis in the males was observed. However, their libido appeared to be reduced. None of the males achieved a mating during and after the period of medication.     

Influence of season of birth on onset of gonadotrophic and ovarian functions in young doe hares (Lepus europaeus).

The pituitary and ovarian responses to a monthly i.v. injection of 5 micrograms luteinizing-hormone-releasing hormone (LHRH) were studied in three groups of young doe hares, born in January-February (group I), in April (group II) or at the end of the breeding season (August-September, group III). The LHRH injection was always followed by a release of LH and progesterone, which did not differ among the three groups at 3 months of age. The pituitary and ovarian responses to LHRH increased gradually from the age of 3 months in groups I and III and from the age of 9 months in group II. One female of the ten born in January-February ovulated and reached puberty in June, at the age of 4 months, but with a weak pituitary response. The females born in April displayed a seasonally delayed puberty, at 9 months of age (two of five females ovulated in the next January). Four of the five females born at the end of the breeding season ovulated after LHRH when 5 months old (in February), with a full pituitary-ovarian response. The low pituitary response of group I in June-August, even if 10-20% of females ovulated after LHRH, suggests a need for a period of short days. Then, the most favourable conditions for the hare to reach puberty would be a period of short decreasing daylengths during the fall, followed by increasing daylengths after the winter solstice.