Evaluating the success of translocating Red Kites Milvus milvus to the UK

Abstract

In an attempt to extend the breeding range of the Red Kite within the United Kingdom, 93 (48 males and 45 females) juvenile Red Kites, originating from Spain, Sweden and Wales, were released in southern England in 1989–94, and 93 (52 males, 40 females and one unsexed) juvenile Red Kites, originating from Sweden, were released in northern Scotland in 1989–93. Minimum estimates for first-year survival were 83.1% and 78.0% for male and female Red Kites in England, and 50.0% and 52.5% in Scotland, respectively. Annual survival then improved in the second and third years. Several sick or injured birds were recaptured, treated and returned to the wild, and some of these eventually bred. In their first year, birds released in Scotland tended to disperse greater distances than those released in England, females travelled further than males, and birds released during the early years dispersed further than those released during the later years. Successful breeding started in 1992 in England and Scotland. The mean age of first breeding was 1.9 years and 2.6 years for males and 1.8 years and 1.7 years for females in England and Scotland, respectively. There was a minimum of 59 clutches laid in England and 29 in Scotland in 1991–95. Clutch size averaged 2.9 (England) and 3.0 (Scotland), fledged brood size per breeding pair was 1.9 (England) and 1.6 (Scotland), and fledged brood size per successful pair was 2.3 (England) and 2.2 (Scotland). Demographic parameters were used to construct deterministic models for population growth. At current rates of growth, it is predicted that the English and Scottish populations will exceed 100 breeding pairs by 1998 and 2007, respectively.