Meyburg, B.-U., F. Ziesemer, H. D. Martens & C. Meyburg 2010. On the biology of the Honey Buzzard (Pernis apivorus) - Results of Satellite Tracking. 7th International Symposium "Population Ecology of Raptors and Owls", Halberstadt, Germany, 21.-24.10.2010: Poster.

Poster with all figures:

http://www.raptor-research.de/pdfs/a_sp100p/a_sp148_Meyburg_2010_Honey_Buzzard.pdf

Introduction

European Honey Buzzards are long distance migrants. Little is
known about the migration of German breeding birds. Many
questions can be answered with the help of satellite telemetry,
using state-of-the-art GPS transmitters, which were available to
us from 2009. These included questions on habitat use, home
range size and flight height and speed etc.

Methods
In the time frame 2001 to 2010 we fitted nine adult German
Honey Buzzards (six males and three females), primarily in
Schleswig-Holstein, with solar cell powered satellite transmitters
(PTTs), of various types and producers, weighing 18-22 g. Ten
transmitters were used. In the last two years 3 male birds were
fitted with GPS transmitters, in 2010 one of theses birds with a 3-
D transmitter, which also transmits data on flight height, speed
and direction. The 2-D transmitters used in 2009 transmitted only
GPS fixes but no other data. A female was caught again after
three years and fitted with a new transmitter. A male was also
retrapped after two years but the transmitter was not replaced as
it was still in good working order.

Results
Signal transmission lasted up to three years. With the exception
of the last fitted transmitter with GPS location data was
transmitted almost only during migration. Outside migration
periods the birds probably remained in vegetation that was too
dense to allow the transmitters to be adequately recharged.
Migration
We were able to record up to six complete autumn and spring
migration routes of individual birds. There is no previous
description in the relevant literature of pre-nuptial migration of
European Honey Buzzards fitted with satellite transmitters. For
two of the years both members of a pair could be studied. They
migrated separately and wintered far away from each other. All
birds migrated to West Africa.
The second longest migration route was taken by a male with
transmitter No. 57029 that flew 7,7612 km as far as Gabon (see
Fig. 6). It covered on average 167 km daily. With the exception
of male No. 52033 it is the only Honey Buzzard to date that has
crossed the Equator.
Data on flight height and speed became available for the first
time on autumn migration 2010 (for male No. 52033). It reached
its highest flight altitude over the Sahara at 1,703 m ASL at a
flight speed of 60 kph. The fastest flight speeds (72 und 76 kph)
were also recorded here. Speeds of between 60 and 70 kph
were recorded on seven occasions. The Honey Buzzard spent
the night of 10/11 September at a height of 1750 m ASL in the
Pyrenees.
Two birds perished on migration while crossing the Sahara and
Mediterranean respectively.

Wintering
In so far as the birds could be tracked as far as their wintering
area, four Honey Buzzards spent the winter in Nigeria and one
each in Gabon, Guinea, Cameroon, the Congo and Liberia.
Male No. 52033 wintered furthest south (2°22‘S/ 12°42‘) in
Congo (Brazzaville). Of the birds that were tracked more than
once as far as their winter quarters it was established that they
returned to the same areas. The home range size in the
wintering area was determined for the first time with the
assistance of GPS telemetry (see Fig. 2).
Behaviour in the breeding area
The main diet is the larva of ground-dwelling wasps. They build
their nests above all in woodland, but also in countryside border
structures (hedges, woodland fringes, waysides etc.), and to a
lesser extent in open areas. The GPS fixes were accurate
enough to enable the dug-out wasps’ nest to be found in some
cases.
The core area of foraging can change in the course of the
breeding season. Male No. 95770 for instance daily sought out
a piece of woodland 17 ha in size from 12 to 25 August 2009
but in the preceding period from 19 July to 11 August not at all.
We found three exploited wasps’ nests there.

The birds sometimes spent the night in their foraging areas in
close proximity to the wasps‘ nests found (Fig. 9), which had
probably not yet been completely exploited.
The home ranges of neighbouring pairs overlap to a great extent
and aerial territorial conflicts are common. They help patient
observers to determine the distribution of territories.