VHF radio telemetry monitoring of satellite marked migrating Black Storks (Ciconia nigra) across the Straits of Gibraltar
Cristina Parkes(1), Asociación Amigos de la Laguna de la Janda (2).
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1 Finca El Bornizo, 11390-Pelayo. Cádiz. Spain. crispak@eresmas.com
2 Cortijo de “La Haba”. 11392 Tahivilla. Cádiz. Spain.
INTRODUCTION
The migration of birds. has always remained a great mystery to mankind. It has only been in recent years, due to the ringing and recuperation of rings, that we have gained more knowledge about their movements, migration, wintering areas, lifespan... Due to latest techniques of tagging or fitting birds with satellite transmitters and VHF, we now have very accurate information not only about their migratory patterns and behaviour but about their exact wintering areas and breeding grounds after their long an precarious journey. Added information from the satellite shows us the length of their journey, stopovers for resting an the distances traveled daily.
Black Storks from western Europe use the Straits of Gibraltar for their crossing, the being the stretch of water which divides the continents of Europe and Africa, which makes it one the most important migration routes, together with the Bosphoros for the Eastern population
A small group of ornithologist have, since 1994, been continuing the work started by Cesar San Segundo, collecting data and counting the number of Black Storks crossing the Straits of Gibraltar during the postnuptial migration from August to October. (See table 1)
During the 1995 count, we managed to spot two birds with transmitter on their backs. After contacting several organizations -specially ADENEX- we traced these birds’ country origin. One was a juvenile Belgian bird (which perished near Fez, Morocco), an another one was a female adult from Czech Republic. They belonged to two projects “Cigognes Sans Frontieres” from France, Belgium and Luxembourg and “Africka Odysea” from Czech Republic, whose veteran stork “Krystina” made the crossing as far as we can establish , over eight times before meeting her end in Senegal in 1999. During the 1998 we managed to track two birds with transmitters.
METHODOLOGY
Observers waited in two traditional stations for sighting passing birds. When a black stork was observed then a manual scan between the preset frequencies was taken.
Receiving equipment include a fixed antenna (Diamond 2.7m 5/8CP22E), two scanners (AOR 8000), and two car antennae.
The duration of the study was of 18 days, from September 13 to October 4. There was a total of 102 hours coverage at an average of ten hours per day.
RESULTS
In 1999, due to improved equipment and support from volunteers, we were able to track fourteen storks (see table 3). Out of six Czech birds two crossed the Straits and twelve of the “Cigognes Sans Frontieres” made the crossing. Each bird had to be scanned through all the frequencies as some birds, like those from Belgium, had problems with the Argos satellite transmitters and no location was received. Only VHF devices worked correctly.
The stations used were: Algarrobo in the eastern sector and Cazalla in the Western sector. Depending on the prevailing winds (see table 4) and climatic conditions, one or other were used (see graph 1). There was also a station a t the top of the Rock of Gibraltar and Hermanillas. They were used on several occasions.
Also noted were the meteorological conditions, single and bird groups, routes taken, time and duration of signals. The total numbers of storks seen was 986. (see table 2).
The strength and the direction of winds are the main factor on, how, where and when the birds decide to set off to their journey towards Africa.
Over the numbers of years that we have been involved with counts through the Straits of Gibraltar, we have observed when the wind and weather conditions are adverse and very unstable, the birds try through the day to make the crossing. Suddenly, a spell of improved weather conditions sets in, and they make their crossing over the stretch of water to the Moroccan coast. If the attempts of the crossing fails, they usually make for the hinterland, having exhausted that day’s possibilities and usually wait until the following morning before trying again.
CONCLUSIONS
The birds are in greatest danger from poison, electrical power line and, of course, illegal hunting specially in France, Italy and Spain. Birds with transmitters give us the information on how and where these birds meet their sad end.
REFERENCES
BERNIS, F. (1980). La migración de las aves en el Estrecho de Gibraltar. Vol.' 1: aves planeadoras. Universidad Complutense. M a d r i d
SAN SEGUNDO,C. (1994). Recuento de cigüeñas negras en migración otoñal por Gibraltar. Quercus nº 102:13-16.
SEO/Birdlife (1997, 1998). Programa MIGRES, Seguimiento de la Migración en el Estrecho. Informes Otoño 1997 y Otoño 1998.
PARKES, M.C., LOBÓN, M, JIMENEZ, J.M., Censo Migratorio Postnupcial de la Cigüeña negra en el Estrecho de Gibraltar 1995-1996. Almoraima 19.
Acknowledgments: Alejandro Torés Ruiz and Alejandro Torés Sánchez for their technical help and support. Christa Buehrer and Judit Szabo for their enthusiasm, friendship an love of Black Storks. All members of the MIGRES project, the GOHNS from Gibraltar -specially Paul- and everyone who helped us. A very special thanks to Krystina from Africka Odysea project who gave so much satisfaction over the years. She was who motivated us to continue our studies and our fascination with these wonderful birds.
Tables y graphs.
Table 1. Posnuptial Black Stork migration across the Straits of Gibraltar. Crossed birds.
Year
Birds
Year
Birds
1993
943
1997*
1469
1994
986
1998*
1141
1995
1358
1999
986
1996
1707
* Data from MIGRES Project
Table 2. Sight birds at every observatory
Algarrobo
Cazalla
Gibraltar
Hermanillas
Bujeo
Whole day
13/9/99
27
109
136
14/9/99
17
78
95
15/9/99
110
4
114
16/9/99
21*
21
17/9/99
41*
2*
43
18/9/99
33*
33
20/9/99
104*
104
21/9/99
123*
123
22/9/99
23
23
23/9/99
67
67
24/9/99
19
19
25/9/99
1
1
26/9/99
48
48
27/9/99
8
51
13
72
28/9/99
46*
46
29/9/99
1*
1
30/9/99
34*
34
4/10/99
6
6
Total
608
296
21
48
13
986
* Stork with transmitter (see table 3)
Table 3. Date when black storks with transmitter crossed.
Black Stork
Observatory
Hour
Remmarks
16/9/99
Dominika1
Gibraltar
13:30-13:45
Última localización recibida el 15/9/99
17/9/99
Maria2
Algarrobo
09:30-09:40
Signal also at Cazalla from 9:30 to 10:24
Valerie2
Algarrobo
09:30-10:24
Signal also at Cazalla from 9:30 to 10:24
18/9/99
Naussica2
Algarrobo
09:55-10:03
10:35-12:07
Randomly signals until 15:36
20/9/99
Martha2
Algarrobo
15:30-15:50
21/9/99
Julien2
Algarrobo
08:35-08:45
Marie2
Algarrobo
09:15-09:40
Aube2
Algarrobo
09:35-09:51
28/9/99
Luis2
Cazalla
14:44-15:05
29/9/99
Carol2
Algarrobo
08:40-11:00
Krystof1
Algarrobo
13:38-14:10
Probably crossed thru Gibraltar.
30/9/99
Johanna2
Algarrobo
11:45-14:40
Lisa2
Algarrobo
15:45-14:40
1 Belongs to Africká Odysea Project; 2 Belongs to Cigognes san Frontiers Project
Table 4. Number of birds crossed at every observatory depending wind direction.
Algarrobo
Cazalla
Gibraltar
Total
Easterly
175
6
181
Westernly
374
2
21
397
Graph 1. Sigthnigs percentage at every observation point.
