Fw: Phorusrhacids - a modern equivalent?

[Ronald Orenstein <ron.orenstein@rogers.com>]

According to the archive hte following has still not shown up properly on the 
list -- my apologies if it has, but I'm trying again!


To my eye, the bird with the most similar beak to a phorhusracid today is 
Steller's Sea Eagle (Haliaeetus pelagicus); see 
http://animals.nationalgeographic.com/animals/birds/stellers-eagle.html.   For 
a paper on this bird's diet see 
http://www.wbsj.org/nature/kisyou/eagle/pdf/diet.pdf (but it says nothing about 
its beak).  The abstract reads:

Qualitative data on the diet of adult and young Stellerâs Sea Eagles Haliaeetus 
pelagicus in North Okhotia during spring (incubation period) and summer (chick 
rearing period) have been analyzed. The total of 177 prey samples containing 
551 prey items from nests located on rivers, seacoast and on islands with large 
sea bird colonies were analyzed. The diet of Stellerâs Sea Eagles consists (in 
descending order of importance) of birds, ïsh, mammals, and carrion. Birds 
dominate the diet of the coastal pairs (73%, N = 107), especially in the pairs 
breeding at the sea bird colonies (91%, N = 211). The proportion of birds in 
the diet of eagles nesting on rivers is much lower (11%, N = 38). In summer ïsh 
is a dominant component of diet only in riparian pairs (77%, N = 78). In 
coastal pairs, as well as in pairs at the seabird colonies the proportion of 
ïsh was lower: 26% and 7% (N = 28 and 19) respectively. Carrion is very 
important for Stellerâs Sea
 Eagles in spring. In nests along rivers 83% (N = 6) of prey in spring is 
carrion from traps set by trappers. In spring the eagles occupying riparian 
nest sites consume mostly mammals and carrion, whereas on the coast eagles feed 
on birds. In summer the riparian pairs switch to ïsh, whereas coastal nesting 
pairs consumed mostly birds, although the ïsh component increased also. The 
composition of the diet of chicks was dramatically different between habitats. 
Chicks reared in riparian nests have ïsh-oriented diet, whereas chicks reared 
in coastal nests eat mostly birds. At sea bird colonies the Stellerâs Sea 
Eagles selected species that were extremely abundant and were relatively less 
manoeuvrable in ïight.

However, a paper from the same symposium (The morphology of the bill apparatus 
in the Stellerâs Sea Eagle, by Alexander Ladyguin) examines the bird's skull 
morphology and illustrates its skull; see 
https://www.wbsj.org/nature/kisyou/eagle/pdf/morphology.pdf.  The author notes:

"...The upper jaw in Stellerâs eagle is extraordinarily massive when compared 
to those of other sea eagles, its depth accounting greatly for the massive 
appearance.

"Birds jaws are powerful âtoolsâ used for feeding, especially in the birds of 
prey. The Stellerâs eagleâs strong, very curved bill is the perfect implement 
for food ripping and tearing large carcasses into small pieces that are easy to 
swallow. The main food of Stellerâs eagle are large ïsh, sometimes weighing 
about 6-7 kilograms, similar to the eagleâs own mass. In the Bering and 
Ochotskoe seas the main ïsh species upon which they feed are the anadromous 
salmon. Fish skin is tough and difficult to tear. But ïeld observations suggest 
that Stellerâs Sea Eagles can consume about 900 g of ïsh in 3-4 minutes. In 
comparison, White-tailed Sea Eagle feeding at the same locations spend about 18 
minutes to consume the same amount, and Golden Eagle requires 28 minutes 
(Ladygin 1994, 1996)."

'Food ripping" involves holding food down with the foot a
 rapid food handling may be advantageous in competing for food with other 
eagles at feeding aggregations.  If this is in any way analogous to 
phorhusracids, perhaps these birds used their beaks not so much for killing but 
for ripping already-killed items (or scavenged carcasses) to pieces, and if the 
birds tended to squabble over carcasses the bird with the best ability to tear 
chunks of food away in a hurry may be at an advantage.
 
 
Ronald Orenstein
1825 Shady Creek Court
Mississauga, ON L5L 3W2
Canada

 Ronald Orenstein
1825 Shady Creek Court
Mississauga, ON L5L 3W2
Canada