Zur Mauser des Großgefieders beim Seeadler (Haliaeetus albicilla) in Schleswig-Holstein

Abstract

Flight feather moult of White-tailed Eagle (Haliaeetus albicilla) in Schleswig-Holstein, GermanyBetween 1955 and 2000 feathers moulted by White-tailed Eagles were collected systematically in the breeding territories in Schleswig-Holstein, Germany. 581 tail feathers and 382 primaries from a maximum of 22 nest sites (1999) and more than 300 secondaries (8 ! collected between 1960 and 1970) were considered. Moulting process of primaries and secondaries is serially continuous, with several moult waves proceeding simultaneously through separate moult units in each wing. Tail feathers were moulted in sequence of 1-6-3-4-2-5 and showed a predominantly transilient alternation. Although tail and flight leathers could be moulted in any month between April and October, there was a strong tendency for them to be moulted between May and August. The plumage characteristics of 18 dead eagles of known age were also examined. Up to and including the 4th moult (in the 5th calendar year), tail moult was almost complete each year. Adults generally moulted their tail feathers over a 2-year period with an annual moult rate of 53 %. Serial moult of primaries in immature eagles normally was completed within a range of 2 rarely 3 years (annual rate = 49 %). Primary moult in adults took place over 3 (occasionally 4) years. Annual rate for flight feathers of adults (in the 5th moult and later) was 46 %. In Schleswig-Holstein the annual rates for tail and flight feathers were on average higher than those in Finland and Sweden, probably because moulting season there is shorter than it is in Schleswig-Holstein because of the different amplitudes of the photo-period in the two regions on different latitudes. Moult patterns were modelled to demonstrate the influence of breeding status, weather conditions and food availability on annual rate. According to this model females showed a higher annual moult rate of primaries and tail feathers in years without breeding success. Tail and flight feathers were moulted on average 1.5 months later in years with breeding success than in years without. Sex specific differences are seen only in annual moult rate of primaries under specific conditions. Moulting activity is higher in warm and dry summers than in cold and wet summers. This was confirmed by the examination of the plumage of dead birds.

Ranging Behavior of Non-Breeding and Breeding Adult White-Tailed Eagles

“…Despite being adults, they did not differ substantially from dispersing juveniles from the Czech Republic, Austria, and Hungary, who roamed over an area of 13, 376 km 2 (median 95% mcp) [29]. Ranging data suggested that immature eagles roamed relatively vast territories, but subadults in their fourth calendar year began seeking breeding territories, often in proximity to their natal sites, and some even initiated breeding attempts [17]. It is important to note that these findings were based on ringing recoveries from the period between 1977 and 2006, and the white-tailed eagle population is currently much more saturated, with young adults still in search of territories.…”

“…White-tailed eagles typically commence breeding in their fifth calendar year [15] and attain full adult plumage at that time [16]. However, owing to a substantial increase in their population numbers in recent decades [17][18][19], many adult individuals may still not establish territories, as the age of first reproduction is a density-dependent trait in avian predators [20]. This has led to an increase in the proportion of floaters in the population.…”

GPS Tracking Reveals the White-Tailed Eagle Haliaeetus albicilla as an Ambassador for the Natura 2000 Network

“…While nesting pairs are known to be sedentary, juvenile, immature, and non-breeding, floating adults [11] move over large parts of central and eastern Europe in the course of their natal dispersion [12], which typically lasts several years in this delayedmaturity species [13]. Several studies have examined the process of natal dispersal in whitetailed eagles, and have recorded details such as timing [14], distances travelled [15,16], habitat use [17], degree of fidelity to the natal area upon recruitment [18], and the potential of human-wildlife conflicts associated with wind energy [19]. White-tailed eagles begin their dispersal from July to October of their hatch year [12] and breed in their fourth calendar year at the earliest [20].…”

Experimental evidence that a large raptor can detect and replace heavily damaged flight feathers long before their scheduled moult dates

“…Secondly, flight feather renewal requires proportionately more time for large than for small birds because the growth rate of flight feathers increases only about half as fast as does the length of the flight feathers when these variables are scaled to body mass (Rohwer et al 2009). Thus, large birds that fly while moulting often carry some heavily worn feathers in their wings and tails (Struwe-Juhl & Schmidt 2003, Rohwer et al 2011.…”

“…). Thus, large birds that fly while moulting often carry some heavily worn feathers in their wings and tails (Struwe‐Juhl & Schmidt , Rohwer et al . ).…”