The Great Bustard Otis tarda in Morocco: a re-evaluation of its status based on recent survey results
Published: Volume 52(1), June 2005. Pages 79-90.
Aims: Between 1999 and 2005 five spring censuses of the Great Bustard Otis tarda population in Morocco were carried out, one of which (2003) was finally discarded due to bad weather conditions. Some complementary, partial counts in autumn 2000, winter 2001-2002 and spring 2004 were also carried out. The aims were to survey new areas where occurrence of the species was suspected but not confirmed, re-evaluate all recently published counts, establish reliable productivity, sex-ratio, and age structure values, and assess the conservation status of this endangered population.
Results and Conclusions: Seven leks were identified, two of which had not been described in earlier studies (Chekbouchan, Mrhitane). The total numbers of birds counted in spring varied between 70 and 84. Based on these, 80-113 birds were estimated in Morocco. The annual estimates of 99, 98, 90 and 80 birds, respectively for 1999, 2001, 2002 and 2005, suggested a decline in numbers throughout the study period, particularly at the two northern leks. Compared to the scarce data from previous decades, these counts suggest that the population has suffered a moderate decrease. The sex-ratio was extremely female-biased, with 3.9 observed and 4.1 estimated females per male. The age structure of the male population was remarkably young, with 23.5% immature males (range 11.1-33.3%), a higher proportion than that recorded in Iberian populations of the species. Average annual recruitment was 0.10 juvenile birds survived up to March from the previous breeding season, per adult female (range 0.045-0.178), a reasonable value compared to Iberian populations. These data suggest that Moroccan Great Bustards are subjected to high adult male mortality. This was corroborated with numerous well-documented cases of illegal hunting. Poaching was identified as the main current threat for the population, followed by collision with powerlines. It is suggested that poaching, and particularly male trophy hunting, has caused the decreases in numbers observed at some leks during the present study. Other threats include the foreseeable extension of the powerline network, and the agriculture intensification at current breeding areas. Immediate conservation actions are urgently required to save this extremely endangered population from extinction.