BOOTED EAGLES: VALIENTE AND LUNA

Booted Eagle (Aquila pennata). Valiente, male (photo: Domingo Rivera).

In 2011 the MIGRA project of SEO/BirdLife started, dedicated to the study of the migration of birds from Spain and using, amongst other methods, satellite transmitters to track the movements of many individual birds. One of the first species involved was Booted Eagle (Aquila pennata), with 15 tagged individuals up to 2013 from various parts of Spain, including four from Extremadura, as part of a project led by the Government of Extremadura. In 2011 six birds were tracked and in 2013 it was eleven, now only ten because of the first tagged birds, a male called Valiente, was found dead, hit by a vehicle, a few weeks ago. The peculiarities of the first journey taken by Luna and Valiente, the first Booted Eagles from Extremadura that were tagged in 2011, were described before in this blog ( autumn journey and winter and spring return) and so we will not repeat the details.

Valiente was an adult male dark morph Booted Eagle tagged at La Roca de la Sierra, Badajoz on 3rd August 2011 and whose transmitter continued to show his location until 4th August 2013, two years and a day later, when he was killed on a road between orchards in Valdelacalzada, Badajoz. A cyclist discovered the corpse and was surprised to find it was ringed and carried a yellow apparatus on its back, which he removed and returned. Domingo Rivera and Ángel Sánchez told us of his breeding history over the last three years. In 2011 Valiente successfully raised on his own a chick, as his mate had died on a wire when the chick was only a week old. In 2012, he took over a Raven’s nest in a eucalyptus tree, paired with a pale phase female and despite building a further two nests failed to breed. In 2013, he failed to pair and travelled in an erratic fashion over the area where he normally bred. With respect to his migrations, the map above shows the journeys in 2011/12 and 2012/13, very similar to each other. In both cases, he wintered in the same general area: once in Niger and the other time in Nigeria. The two-way journeys across the Sahara showed that the return journey was always to the west of the route taken in the outward journey. As can be seen in the graph below, the dates did not vary much, the 2012 journey was a bit earlier than 2011 and he spent more time in 2012 on his wintering grounds in Niger. The return journeys were almost identical in terms of dates and duration. Compared with other tagged Booted Eagles, Valiente had been unusual, being the only one with two wintering zones, one that had wintered further away (3,500 km) and the fastest in its return journeys. Of the four tagged birds from Extremadura, he was the only one that wintered in the eastern Sahel, the others staying much further to the west, between Mali and Mauritania.

Luna is an adult female dark morph, tagged in Alburquerque (Badajoz) on 3^rd August 2011 and whose transmitter continues in operation. Domingo Rivera and Ángel Sánchez again describe her breeding history over the last three years. In 2011, she raised two chicks in a nest in a eucalyptus tree. In 2012, she occupied the same nest, but following its collapse because of weather conditions, she did not raise any young. In 2013, she moved to a new nest in a cork oak where again she raised two chicks. With respect to migration, the map shows the journeys made in 2011/12 and 2012/13. In both cases, she wintered in the same zone between Mali and Mauritania, some 2,500 km from the nest site, and, as with Valiente, the outward journey was more eastern than the return. In the graph below, the most interesting is that the departure date was much earlier in 2012 (5^th August, a month earlier than usual). This was not seen with the other 15 tagged birds and in principle could have been explained by the breeding failure that year. However, that may not have been the reason, because in 2013, Luna also departed very early (2^nd August) despite having a successful season. The return in 2013 was also earlier than in 2012, but by only a week.

The other two Booted Eagles from Extremadura that have been followed are a pair and they breed in the municipality of Badajoz, their names are Guadiana (male) and Alqueva (female). Both are pale morphs and in general their migratory behaviour has been similar to that of Luna, apart from the departure dates, with similar routes and wintering areas in the western Sahel (Mali and Mauritania).

BOOTED EAGLES: THE HOMECOMING

A few weeks ago we spoke in this blog entry about the African odyssey of two satellite-tagged Extremadura Booted Eagles (Hieraaetus pennatus) from September 2011 to February 2012. Like the other tagged birds in other Spanish provinces our two Booted Eagles have now come home safe and sound and seem to have got down to the task of breeding. Their return journeys were as follows.

Luna (a female, No.5 on the map) left her stable wintering area in Mali on 16 March. After passing through Mauritania, Western Sahara and Morocco she crossed the Strait of Gibraltar on 1 April, thereafter returning more slowly to her breeding territory in Alburquerque (Badajoz), where she arrived on the 6th. In total a 2700 km journey in 21 days at an average of 130 km per day and the longest stages of 344 km and 323 km on 18 and 20 March, smack in the middle of the desert. Progress within Spain was much slower, with a maximum daily stint of 120 km. In 2012 she has built a new nest only 250 m from the one used in 2011, which fell down last winter (Ángel Sánchez, pers. com.). 

Valiente (male, No.6 on the map) kicked off his trip from Nigeria on 19 March, then passing through Niger, Mali, Algeria and Morocco, crossing the Strait on 2 April and arriving back in La Roca de la Sierra (Badajoz) on 7 April. A long journey of 3500 km in 20 days, at a mean speed of 175 km per day and the longest stages of 420 and 418 km on 21 and 24 March. The longest day journey made in Spain was only 95 km. This was the swiftest moving of the six birds and one of the two with the most distant wintering area.

If we look at the whole set of six tagged birds (two in Badajoz and Madrid and one each in Castellón and Ávila) we find that the spring homecoming journey did not follow the same route as the autumn outgoing one, which was further west in all cases. The start day varied from 1 to 20 March (mean date of 13 March), the Strait crossing from 30 March to 11 April (mean date of 4 April) and the arrival on the breeding territory from 4 to 26 April (mean date of 10 April). The total distance covered ranged from 2725 to 3530 km (mean of 3095 km), the duration from 17 to 51 days (28 mean) and the average daily speed from 70 to 175 km (mean 126). Barring one bird that made the trip in two stages, stopping for a time in one of its two wintering areas, the rest came back directly, moving more rapidly through Africa and slowing down upon entering the Iberian Peninsula.

More information on the SEO/BirdLife project website "La migración de las aves" (Bird Migration).

TWO SATELLITE-TRACKED EXTREMADURA BOOTED EAGLES

Booted Eagle (Hieraaetus pennatus). Brava, adult female fitted with a satellite transmitter
and released at Los Canchales Reservoir, Badajoz. By Ángel Sánchez.

An ambitious SEO/BirdLife bird migration project kicked off in 2011, its remit including satellite tracking. One of the star species is Booted Eagle (Hieraaetus pennatus). The movements of six tracked birds can now be followed live on internet (click here). Two of these birds, forming part of a project being run by Junta de Extremadura, were the first to begin their autumn migration and reach their African destinations in 2011. The return spring migration is now underway, so it's the perfect time to report the movements to date of both Extremadura eagles.

Booted Eagle (Hieraaetus pennatus). Luna, female, on the left, and Valiente, a male, are the two Extremadura-nesting satellite-tracked birds (photos: SEO/BirdLife).

Luna is an adult female Booted Eagle nesting in Alburquerque (Badajoz). On 03.08.2011 it was fitted with a satellite transmitter to keep track of its movements thereafter. On the project website it wears the number 5. After the transmitter was fitted, it remained in its territory until setting out on its migration odyssey on 07.09.2011. On 10 September it crossed the Strait of Gibraltar and two days later reached the dreaded Sahara. There it picked up pace, putting in its two longest daily stages: 370 on 12 September and 403 km on 17 September. At last, on 19.09.2011, after a 12-day trip it reached its wintering quarters in the Sahel, over 2500 km from its nest (an average of 204 km a day). Since then, and at least until 01.03.2012, it pretty much stayed put, spending over five months in an area straddling Mauritania and Mali.

Autumn migration of six satellite-tracked Spanish Booted Eagles (Hieraaetus pennatus) in 2012 (http://www.migraciondeaves.org/).

Valiente, wearing number 6, is an adult male Booted Eagle nesting in La Roca de la Sierra (Badajoz). It was also fitted with its transmitter on 03.08.2011 and then set out on its long journey to Africa a little later than Luna, on 13.09.2011. Like Luna it reached the Straits in three days but then needed 15 to reach the Sahel on 02.10.2011. Its pace was a bit slower (18 days, averaging 151 km a day), putting in its longest stage of 301 km on 23.09.2011. At first it settled down in Mali, 2700 km from home, but then moved southwards, first to Niger (15 October) and then to Nigeria (16 November), 3500 km from home, where it remained on 01.03.2012. Of the six Booted Eagles tracked, only one other bird wintered in two different spots, in this case reaching Sierra Leona, 3530 km from its nest. Both made the longest trips, while the other four have spent five months in the same zones.

Lastly, the third Eagle tracked, not featuring on the project website, was an adult female called Brava, from the Los Hornos Wildlife Refuge Centre (Sierra de Fuentes, Cáceres). The bird was released at Los Canchales Reservoir on 24.09.2011. It instantly flew southwards. Once at the straits it struck off over the sea but seems to have foundered somehow about 30 km northeast of Ceuta, transmitter signals ceasing on 06.10.2011.

THE BOOTED EAGLE IN EXTREMADURA (2009-2010)

Booted Eagle (Hieraaetus pennatus), light phase. Portaje, Cáceres, 27-07-2010. By Eva Palacios.

The Booted Eagle (Hieraaetus pennatus) was one of the target species in the SEO/BirdLife-brokered national woodland raptor survey 2009-2010 (Palomino and Valls, 2011). The estimated Extremadura population came out as 2210 territories (range 2150-2270). This represents 12% of the Spanish total (18,500 territories), ranking fourth after three bigger regions: Castilla y León (3820), Andalucía (3790) and Castilla-La Mancha (3020). Extremadura's mean density is 5.3 territories per 100 km2, the highest in the whole country and way above the national mean (3.7). Behind Extremadura come Andalucía, Aragón and Castilla y León (densities of from 4.1 to 4.3).

Badajoz, with an estimated 1200 territories, boasts Spain's biggest provincial population, followed by Cáceres with 1010 territories. The highest provincial density is recorded by Sevilla (5.8), followed by Badajoz (5.5), Huelva (5.11) and Cáceres (5.08), all in the southwest quadrant of mainland Spain.

The Booted Eagle's range takes in the whole of Extremadura; it seems to be commonest in the northern half of Cáceres and scarcest in the centre-west of Badajoz. In all it was recorded in 57% of the grids with lookout points (65% in Cáceres and 52% in Badajoz). The Booted Eagle is a very versatile raptor. In Spain it prefers inland areas with cool, sunny springs, moderate relief and not too much farmland.

Predictive map of the Booted Eagle's range in Spain, taken from Palomino and Valls (2011).

The car transects threw up an average of 4.4 birds every 100 km; it was observed in 77% of the sampled grids (83% in Cáceres and 71% in Badajoz). The mean birds-per-kilometre figure for Spain as a whole was 2.3, led by Salamanca (5.7), Valladolid (5.6), Segovia (4.8), Cáceres (4.5), Granada (4.5) y Badajoz (4.2).

The Booted Eagle's trend in Spain is a very sharp increase according to the breeding birds monitoring project SACRE, with a 43% rise from 1998 to 2010. In the central zone of Spain, including Extremadura, the increase is even higher: 53%. Gibraltar Strait counts of migrating birds have also multiplied fourfold since the 1990s, with almost 30,000 Booted Eagles being recorded nowadays (Fundación Migres).

As regards the figures thrown up by this survey, not much can be said because there is insufficient previous information to go on. Nonetheless some discrepancies are evident in the above paragraphs. The population estimates clearly bring out the importance of the southwest quadrant of mainland Spain (Extremadura and Western Andalucía), while the observation probability map (bound up with abundance) shows the highest probabilities in Cáceres and the south of the northern meseta. The same goes for the car transects, with highest bird-per-kilometre figures in the northern meseta. In both cases Salamanca comes out winning while Badajoz and Sevilla come out losing.

The fieldwork was coordinated and carried out by SEO volunteers and staff of the Environment Board of the Regional Council of Extremadura.

Source:
- Palomino, D., y Valls, J. 2011. Las rapaces forestales en España. Población reproductora en 2009-2010 y método de censo. SEO/BirdLife. Madrid. [PDF]
- Fundación Migres: http://www.fundacionmigres.org/Noticia_aumento_poblaciones_rapaces.html