SHORT COMMUNICATIONS 
175 
(Horvath 2009). All three young successfully 
fledged and left the nest. Three more cases in 
which young Common Buzzards were found in 
White-tailed Sea Eagle nests originated also from 
Hungary (Palko 1997, Fenyosi and Stix 1998, 
Horvath 2006). 
Interspecific brood parasitism, placement of 
nestling hawks in eagle nests by humans, and non- 
lethal predation followed by parental care have 
been considered as causes of this phenomenon for 
young Red-tailed Hawks adopted in Bald Eagle 
nests in North America (Stefanek et al. 1992, 
Watson et al. 1993, Watson and Cunningham 
1996). Interspecific brood parasitism has not been 
recorded in the Accipitridae (Yom-Tov 2001), and 
this scenario was considered unlikely for the cases 
of adopted nestlings of Red-tailed Hawk (Stefa¬ 
nek et al. 1992, Watson et al. 1993). We support 
this contention regarding the cases of adopted 
nestlings of Common Buzzards in nests of White¬ 
tailed Sea Eagles. For brood parasitism to have 
occurred, Common Buzzard females would have 
had to enter the eagle nests, contend with an adult 
White-tailed Sea Eagle with newly hatched 
nestlings, and laid its eggs. The eggs would have 
had to be incubated by the adult eagles, the eagle 
nestlings or both. White-tailed Sea Eagles begin 
to nest (lay eggs) in central Europe in February 
and incubation lasts 34-46 days. Common 
Buzzards begin to nest at the end of March and 
incubation lasts 33-35 days. There is no tendency 
among Common Buzzards for brood parasitism 
and the time difference between the start of 
nesting for both species makes brood parasitism 
improbable. Thus, we do not believe brood 
parasitism is a realistic explanation of these 
phenomena. Placing of Common Buzzards nest¬ 
lings into White-tailed Sea Eagle nests by humans 
also was unlikely due to the difficulties in 
climbing the high trees and there is no obvious 
rational reason to do it in different places and 
years. 
The most plausible explanation for these 
phenomena is non-lethal predation followed by 
parental care. This scenario was considered the 
more likely explanation for the occurrence of live 
young Red-tailed Hawks in Bald Eagle nests 
(Stefanek et al. 1992, Watson et al. 1993, Watson 
and Cunningham 1996), and we suggest the same 
explanation for cases in which young live 
Common Buzzards occurred in White-tailed Sea 
Eagle nests. One of the adult White-tailed Sea 
Eagles may have captured the nestling Common 
Buzzard as prey for it own nestlings and failed to 
kill it during capture and transport. Food-begging 
calls of Common Buzzard chicks that survived the 
transport apparently stimulated feeding from the 
White-tailed Sea Eagles (Horvath 2009). The 
adopted Common Buzzards were usually in good 
condition with no apparent signs of abuse by the 
adult or nestling eagles. It suggests the adult eagles 
fed them properly and/or the Common Buzzards 
were able to scavenge sufficient food to stay alive 
and fledge. Corroborating this hypothesis is infor¬ 
mation that birds, including chicks from nests of 
Grey Herons (Ardea cine re a), commonly occur in 
White-tailed Sea Eagle diets (Balat and Belka 2005, 
Belka and Horal 2009, Horvath 2009). The 
presence of raptor species also was found in an 
analysis of Bald Eagle prey items collected at nests 
in the USA (Stefanek et al. 1992). Moreover, 
raptors at times bring prey that is still alive to their 
nests (Spofford and Amadon 1993). In addition to 
Red-tailed Hawks in Bald Eagle nests, another case 
of an apparent nonlethal predation was a Glaucous¬ 
winged Gull ( Lotus glaucescens) chick and subse¬ 
quent adoption by a pair of Bald Eagles as noted in 
Alaska (Anthony and Fans 2003). 
The adoption of Common Buzzard chicks by 
White-tailed Sea Eagles could be explained as a 
parental recognition error because there are no 
benefits for parents to adopt chicks of an unrelated 
species. The Common Buzzard nestlings benefit¬ 
ed, however, from the recognition error of the 
eagles. The White-tailed Sea Eagle and Bald 
Eagle, as are non-colonial bird species, are 
probably unable to distinguish their offspring 
from other species (Alcock 1997). We consider 
this type of adoption as a surprising phenomenon 
in central Europe. Numbers of nesting pairs of 
White-tailed Sea Eagles in the Czech Republic 
and Hungary were relatively low; they numbered 
—50 and 180 nesting pairs in the Czech Republic 
and Hungary in 2007, respectively (Belka and 
Horal 2009, Horvath 2009). Conversely, the 
Common Buzzard is the most common raptor 
species in this area and the last census for a 
nesting population in the Czech Republic revealed 
11,000-14,000 nesting pairs (Stastny et al. 2006). 
We consider noteworthy that this phenomenon 
of interspecific adoption occurs in raptors with 
similar ecological niches in both North America 
and Europe. The Bald Eagle is a North American 
ecological equivalent of the White-tailed Sea 
Eagle, and the Red-tailed Hawk is among the 
most common raptors in North America just as the 
