Estimates of Survival in the Cape Vulture, Gyps coprotheres

Modelling survival rates in the Cape GriffonGyps coprotheres,with emphasis on the effects of supplementary feeding

“…These estimates were criticized& as being far too low and for making the unwar-ranted assumption that survival is constant across all age-classes. Our estimate of constant survival rate (model 1, Table 1) is 68.8%, which is 25% higher than that of Houston.21 Using a much larger data set of ring-recoveries than that used by Houston, 2 I Piper et al 6 estimated survival rates at 17%, 61%, 74% for the first three age-classes. It was shown subsequently that the reporting rate varied among the age-classes and that the methods of analysis were flawed, leading in turn to an underestimate of survival for the first age-class.…”

The influence of non-toxic concentrations of DDT and DDE on the old world vulture estrogen receptor alpha

“…With the majority of dead chicks from the above study showing abnormal bone development (osteodystrophy), a deficiency of dietary calcium was believed to be the underlying cause of both the poor hatchability and rearing success seen in the species (Piper et al, 1981). More importantly, this calcium deficiency was directly related to the encroachment of cattle ranches into the vulture foraging areas (Mundy et al, 1992).…”

“…Unfortunately, despite being very prominent in their environment, the species has steadily declined over the last century with poor fertility, high nestling mortality, African witchcraft, malicious poisonings and pylon/power line injuries being listed as causes (Piper et al, 1981;Komen, 1991;Fernie and Reynolds, 2005;IUCN red list, 2007). Of these, nestling mortalities is probably the most important as estimates in the 1980s placed the survival of first-year nestlings at 17%, with the overall probability of a hatchling reaching three years being 10% (Piper et al, 1981). This low rearing rate is made more extreme when one considers that sexual maturity is only reached at 5 years with only one egg being produced a year.…”

Age-related differences in foraging behavior of Montagu's harrier Circus pygargus males in south-east Poland

“…This refers particularly to begging behaviour, piracy, and scavenging (Witkowski 1989;Kitowski 1994;Bavoux et al 1998), which were observed when harriers were not able to forage themselves. It seems that cultivating such behaviour can have a great adaptive value, being extremely significant in relation to a high mortality of raptors in their first years of life (Piper et al 1981;Schmutz and Fye 1987;Preston and Beane 1993). We suggested that the described infantile begging behaviour also may take place in the wintering area.…”