EXTREMADURA CORMORANT COUNT 2012

A Spain-wide Cormorant (Phalacrocorax carbo) count was carried out in summer 2012. The provisional results for Extremadura, while awaiting publication of the overall data, are as follows.

Three colonies were found with a total of 651 occupied nests. The biggest colony, in La Serena reservoir, was visited twice. It comprises 619 nests in two clusters, the main one with 614 nests on half-sunken Holm Oaks and the other only 2 km away with 5 nests on Eucalyptus. The other two colonies found seem to be new, or at least unrecorded hitherto. One was at Alange reservoir, where a 23-nest Eucalyptus colony was found by chance on 12/07/12 (upper photograph; by Ángel Sánchez). The other new colony was at Alqueva reservoir, again on half-sunken Holm Oaks, with 9 nests counted on three visits from May to June. [Other post on Cormorant in Extremadura]

The Extremadura Cormorant trend is clearly upwards, with an exponential increase in only 10 years. Barring the one-off nest in Valuengo reservoir found in 1993 (Prieta and Mayordomo, 2012), the first Extremadura colony formed in La Serena reservoir in 2002. This colony grew from 10 pioneering pairs in 2002 to 102 in 2007 and 341 in 2011 (including 13 in Córdoba and one in Ciudad Real; Piñeiro, 2011) and 619 by 2012. Unless the final census results prove otherwise, this could well turn out to be Spain's biggest colony today. In 2007 there was a national breeding wildfowl count, including the Cormorant(Palomino and Molina, 2009). The published result included three Extremadura colonies, the abovementioned one in La Serena and another two at River Guadiana in Valdetorres and at Valuengo reservoir. There is however no trustworthy information on these two ostensible colonies, with no indications of actual or recent nesting in 2011 or 2012. The prudent option is therefore to rule them out. In 2012 two new colonies were found, once more on big reservoirs of the Badajoz basin, and regional figures have doubled in a single year. [Other blog entries on the Cormorant in Extremadura]

Collaborators. The La Serena and Alange colonies were found by the Junta de Extremadura: Ángel Sánchez, Domingo Rivera, Sergio Pérez, Miguel Ángel Sánchez, Fermín Sierra, Demetrio Vázquez, Irene Rodríguez, Sandra Blanco, José Manuel Rama and José María Castaño. The Alqueva colony was covered by Luis R. Hernández Díaz-Ambrona and Juan Carlos Panigua (SEO/BirdLife volunteers). 

Sources: 

- Piñeiro, X. 2011. Cormorán grande Phalacrocórax carbo (p. 487). In, Molina, B., Prieta, J., Lorenzo, J. A. and López-Jurado, C. Noticiario Ornitológico. Ardeola 58:481-516. 

- Palomino, D. and Molina, B. 2009. Aves acuáticas reproductoras en España. Población en 2007 y método de censo. SEO/BirdLife. Madrid. 

- Prieta, J. and Mayordomo, S. 2012. Aves de Extremadura, vol. 4. Años 2004-2008. Grupo Local SEO-Cáceres. Plasencia. [PDF]

THE GREAT CORMORANT IN LA SERENA RESERVOIR. 2011

An earlier post of this blog presented the information to hand on the breeding of the Great Cormorant (Phalacrocorax carbo) in La Serena Reservoir. New figures have recently been published in Ardeola, so we hereby update that earlier information.

The Ardeola text ran as follows:
"Count of the breeding population in La Serena Reservoir in 2011 with a total of 341 breeding pairs shared out in five colonies: the biggest lies in the province of Badajoz with 313 pairs; in the same province there are two more breeding clusters with 11 and 3 nesting pairs; one 13-nest colony was found in the Córdoba part and one isolated nest in the Ciudad Real part". This therefore makes a total of 341 total pairs, 327 in Badajoz, 13 in Córdoba and one in Ciudad Real (Xurxo Piñeiro)."

Source:
Piñeiro, X. 2011. Cormorán grande Phalacrocórax carbo (pag. 487). In, Molina, B., Prieta, J., Lorenzo, J. A. and López-Jurado, C. Noticiario Ornitológico. Ardeola 58(2):481-516.

BREEDING CORMORANT COLONIES IN EXTREMADURA

Great Cormorant (Phalacrocorax carbo). Plasencia Reservoir, Cáceres. By Javier Prieta.

The Cormorant (Phalacrocorax carbo) is a recent coloniser in Extremadura. It must have been a scarce winter visitor for much of the twentieth century, becoming common only as from the 1980s (e.g. a count of 804 in 1986). Since then numbers have soared; witness the two national roost-based wintering Cormorant counts, one held in January 1996, producing a figure of 8656 (25% of the Spanish total) and another in January 2003 with 12,265 (18%). In both cases Extremadura was the region with most wintering Cormorants in Spain (Prieta, 2007).

It didn't take long for the first nests to be found in Spain (del Moral and de Souza, 2004). Before 1990 only a few one-off breeders were known from the Medas Islands off the coast of Girona in Catalunya. The first inland record was a failed breeding attempt in Santillana Reservoir, Madrid, in 1989. The first breeding record in Extremadura involved a weakly-flying pair that produced two chicks in Valuengo Reservoir, Jerez de los Caballeros, in 1993 (F. Gragera). Similar one-off cases recurred in other parts of Spain until, in 1997, the first breeding colony was found on Navalcán Reservoir, Toledo. By the beginning of the C21st there were several established colonies, adding up to over 40 breeding pairs. The first Extremadura colony of 10 breeding pairs was found in 2002 on La Serena Reservoir(Prieta, 2007).

Cormorant Colony (Phalacrocorax carbo) on La Serena Reservoir, Badajoz, in 2007 (photos: Carlos Sunyer).

The first and only national count of breeding Cormorants dates from 2007 (Palomino and Molina, 2009), producing a total of 532 pairs in 11 Spanish sites. The main population has built up in Toledo, with 4 colonies and 214 pairs, the lion's share of them in Rosarito Reservoir (202 pairs). Badajoz accounts for the second-biggest population, 3 colonies with 132 pairs: 102 at La Serena Reservoir (on dead Holm Oaks where the River Esteras flows into the reservoir, in the municipal district of Capilla), 26 pairs at the reservoirs of Valuengo and La Albuera (River Ardila, Jerez de los Caballeros) and 4 pairs on the River Guadiana (Valdetorres). The only breeding record in the province of Cáceres was a failed attempt on the River Tagus in the National Park of Monfragüe; a pair built a nest on a dead Eucalyptus tree in May 2006 without any signs of an ensuing clutch (J. Prieta).

By 2011, four years after the abovementioned count, news has come in of the three Extremadura "colonies", although it should be made clear that there has been no official regional count of the species. La Serena Reservoir recorded unprecedented figures. In mid-May Xurxo Piñeiro and María José Valencia counted 250 occupied nests in two colonies: the traditional one on an islet with 240 nests on 29 trees, nearly all Holm Oaks, plus a much smaller colony with 10 more nests. Some days later, on 26 May, personnel from the Regional Council of Extremadura counted 262 occupied nests in the first colony, broken down into 3 subcolonies of 248,11 and 3 nests (Ángel Sánchez, Luis Lozano and Domingo Rivera). This is therefore without doubt one of the biggest, if not the biggest, in the whole of Spain. Conversely, the other two sites recorded in the 2007 count, Guadiana-Valdetorres (Jesús Solana) and Valuengo-La Albuera (Antonio Nuñez), seem to be empty. Or rather they did not even exist any more, since there were no signs of any nests or nest remains in either site. It might well be the case that the so-called colony of the River Guadiana, recorded in 2007, never existed, arising from a mistake in the interpretation of the figures. As for Valuengo, we lack precise information on 2007 and the following years, but it would seem in principle that the 2007 figures were valid.

In sum: the known breeding Cormorant population in Extremadura in 2011 is confined to a single site (La Serena Reservoir) with 272 nests shared out in 2 colonies of 262 and 10 nests. This is the biggest known figure for the species, so the trend is still upwards.

Sources:
- Del Moral, J. C. and de Souza, J. A. 2004. Cormorán Grande invernante en España. II Censo Nacional. SEO/BirdLife. Madrid.
- Palomino, D. and Molina, B. 2009. Aves acuáticas reproductoras en España. Población en 2007 y método de censo. SEO/BirdLife. Madrid.
- Prieta, J. 2007. Aves de Extremadura, vol. 3. Anuario 2001-2003. ADENEX. Mérida

THE CORMORANT AND THE CATFISH

Subadult Cormorant (Phalacrocorax carbo) catching a Black Bullhead Catfish (Ameiurus melas). Galisteo, Cáceres. 02-11-2010 (J. Prieta).

The above sequence of photos shows a Black Bullhead Catfish (Ameiurus melas) being caught and eaten by a Cormorant (Phalacrocorax carbo). The photos would obviously win no prizes; neither is the observation anything out of the ordinary, since Cormorants are skilful fishers. The surprising factor is the place, a recently opened and shallow gravel pit where you wouldn't expect to find fish of this size yet. And the worrying aspect is that this gravel pit should already be occupied by an invasive species that is quickly spreading in native waters. In every single visit to this gravel pit we have seen successful Cormorant captures of Black Bullhead Catfish, which is also a prey species of Little Grebe and several heron species (Grey Heron, Little Egret, Great White Egret).

The Black Bullhead Catfish, native to North America belongs to the siluriformes order, which does not exist naturally on the Iberian Peninsula. Its biggest Extremadura populations are in the catchment areas of the rivers Tiétar and Alagón. As in so many other cases it has been introduced deliberately and also as the accidental result of escaped livebait. There are also records of another introduced North American catfish in Extremadura, the Channel Catfish (Ictalurus punctatus) dating from the 1990s in the Badajoz reservoirs of Zújar and La Serena. Luckily there have been no more recent records. Lastly a third siluriforme, the European Catfish, also called Wels Catfish or Sheatfish (Silurus glanis), has also found its way into some Extremadura reservoirs. In Cedillo there was a one-off record from the 1990s and another was caught in Alcántara reservoir in 2008, this time within the Monfragüe National Park. In this case we are not talking about any old fish but a species that can grow 2.5 metres long and weigh over 100 kg! Native to the large rivers of Central Europe, it is a rapacious predator that has become highly prized by some fishermen, who insist on introducing it illegally wherever they can. Something akin to releasing lions or tigers in our dehesas.

The boom in introduced species contrasts sharply with the lamentable situation of our native species. Largely overlooked, these small denizens of our rivers often turn out to be surprisingly diverse. The latest studies continue to differentiate new species with tiny ranges; endemics have been discovered for Salamanca, Guadalajara and Málaga. In Extremadura the most similar case is the ray-finned species Cobitis vettonica, called Vettonian Spined-loach (Cobitis vettonica) in Spanish. It is exclusive to the catchment area of the river Alagón from which it takes its name, straddling the provinces of Salamanca and Cáceres, with its biggest populations in the rivers Alagón, Jerte and Ambroz.

References: - Pérez-Bote, J. L. 2006. Peces introducidos en Extremadura. Análisis histórico y tendencias de futuro. Revista de Estudios Extremeños 1:485-494 [PDF] - Pérez-Bote, J. L. & Roso, R. 2009. First record of the European catfish Silurus glanis Linnaeus, 1758 (Siluriformes, Siluridae) in the Alcántara reservoir (Tagus basin, Spain). Anales de Biología, 31:59-60. [PDF] - Leunda, P. M. et al. 2009. International Standardization of Common Names for Iberian Endemic Freshwater Fishes. Limnetica, 28:189-202. [PDF]