Summary ECOLOGY BIOB50 - MILLON and Group Sparrow Hawk- UTSC Uoft scarborough

The research study conducted by Millon and group was a long term study which focuses on the growth rate of Eurasian sparrow hawk and their prey community composition.  The main purposes of this study was to determine whether there are changes in the composition of the prey community by analyzing temporal trends within the prey community of the sparrow hawk and how these changes resonate into the dynamics of the sparrow hawk population (Millon 2009). They conducted this study in a vast area in Denmark and visited the breeding areas one to five times annually during the time of breeding (Millon 2009). Then they identified the females who are breeding and aged them using the features of their feathers. Then the researchers obtained the mean temperatures from the meteorological stations and the average temperature of three coldest months in winter and early spring. These periods were assumed the most critical for sparrohawks (Millon 2009).  The diet of the predator was then analyzed during the breeding season and their diet mainly consisted of black bird and skylark. During the years of study, as the abundance of these two main prey species increased, the diet diversity of sparrowhawk decreased (Millon 2009). But then the abundance of these two population decreased during the winter and then the sparrowhawk population also started to declined. The analysis then shows us that the winter climate, and also the prey availability contributes to the population growth and decline of the sparrowhawk population. Prey vulnerability to predation differs according to coloration, behavior, parasite load of prey and can also be altered by changes in habitat structure due to farming practice (Millon 2009). The changes on the composition of these avian prey community shows the variation of prey abundance on predators (Millon 2009). During the mid 80’s when the population of black birds and skylark declined drastically during the harsh winter, the population of the sparrowhawks also started facing a decline in population. Harsh winter climates affecting both the predators and prey species made hunting, food gathering and the maintenance of physiological processed very challenging. Also the data observed during the study explains how the both and predator and prey abundance depends on each other (Millon 2009). In 1987 the skylark population hit rock bottom while black bird population persisted which caused a severe decline in the sparrowhawk population for a brief period and then recovered. Also the use of organochlorine pesticide lead to a decline in sparrowhawk population. “The number of sparrowhawks in the study area fell from 51 to 38 pairs between 1978 – 82” (Millon 2009). This pesticide killed the adult sparrows directly before breeding. The combined effect of predation along with the harsh environmental stressors had been predicted to drive the skylarks to small numbers (Millon 2009). Also the intra-guild predation between northern Goshawk also bought down the growth rate. Northern Goshawk also regularly prey over other raptors including sparrowhawks. Finally, the study revealed that