Lakescape - 554 (Sterna aurantia, Larus ridibundus)

Lakescape - 554 ...

River Tern ...

IUCN Category :
Near Threatened

One of the least studied
Terns ...
They feed mainly by
Plunge Diving ...
... and have specialized
wings for that ...
... called
High Aspect Ratio wings

Formula for getting
the aspect ratio is :

square of wing-length
____________________
Width x 2

High aspect ratio wings,
which usually have
low wing loading
and are far longer than
they are wide, are used
for slower flight ...
This may take the form of
almost hovering
(as used by Kestrels,
Terns and Nightjars) or
in soaring and gliding flight
particularly
the dynamic soaring used by
seabirds ...

I am pleased to put
together this collage
of my images
that nicely shows
this feature of the
Tern's wing ...
... and also allows
comparison with the
very common
Black-headed Gull ...
that does not depend
on plunge dive for
feeding ...

Watch the lovely flight
of this Tern in a
video-clip :
Link :
http://www.birdforum.tv/members/action/viewvideo/10531/River_Tern___feeding_in_flight/
______________

Sterna aurantia

Chroicocephalus ridibundus

Dist. Jhajjar
Haryana
India
20.11.2018