Cattle Egret (Bubulcus ibis). Galisteo, Cáceres. Javier PrietaAs already mentioned in this blog, the National Count of Wintering Herons was held last January. As usual the overall result will be published by SEO/BirdLife. For the moment, however, we can give you a foretaste of the Extremadura results.
The chosen methodology was to count birds in communal roosts. The main date was the weekend 15-16 January, although some counts were held a few days later. No information was obtained for the abundant but non-roost-forming Grey Heron. The same goes for the scarcer heron species (Squacco Heron and Bittern) or the ones that are nocturnal or difficult to detect (Little Bittern).
RESULTS BY SPECIESCattle Egret (Bubulcus ibis). 30,917 birds (22,315 in Badajoz and 8602 in Cáceres) in 38 roosts (23 in Badajoz and 15 in Cáceres). Eleven roosts held over one thousand birds, the standout ones being Azud de Badajoz (6103), River Zújar in Villanueva de la Serena (4200), Valuengo Reservoir (2700), Madrigalejo (2400) and River Guadiana in Montijo (2000). The attached map, plotting the location of the roosts, brings out the obvious importance of the River Guadiana and its surrounding meadows, which account for the lion's share of the regional population.
Little Egret (Egretta garzetta). 1273 birds (823 in Badajoz and 450 in Cáceres) in 38 roosts (20 in Badajoz and 18 in Cáceres). Seven roosts held over 50 birds, the biggest being Valuengo Reservoir (230), Madrigalejo (125) and River Guadiana in Montijo (100).
Great White Egret (Egretta alba). 67 birds in 18 roosts (31 in Badajoz and 36 in Cáceres). The biggest roosts were on the River Tiétar in Malpartida de Plasencia (15), Arrocampo Reservoir (9), Valdecaballeros Reservoir(7) and River Zújar in Villanueva de la Serena (6).
Night Heron (Nycticorax nycticorax). 52 birds in 5 roosts, all on the River Guadiana in the province of Badajoz. The most important roosts were Montijo Reservoir in Mérida (29) and Azud de Badajoz (10).
TREND
There's nothing specific to go on in terms of wintering herons in Extremadura. In January 1992 and 1993, however, two Iberian counts were conducted, giving the results by catchment areas (Fernández-Cruz and Farinha, 1992; Sarasa et al., 1993), but without breaking down the figures by regions or provinces. Working from the maps shown in the 1992 count, we estimate about 53,000 Cattle Egrets and 1500 Little Egrets in Extremadura. The 1993 figures were lower but the estimate is rougher because there is no map to go on; maybe the figures were about 42,000 and 700 respectively.
The number of Cattle Egret roosts has fallen from 64 in 1992 to 37 in 2011, a 40% drop. The fall in the number of birds was similar, about 35% on the mean figure for 1992-1993. This decline is much more notable in the Extremadura part of the Tagus catchment area (-60%) than in that of the River Guadiana (-20%). This figures should not really be taken in isolation, however, since the wintering population of the southwest Iberian Peninsula, including Portugal and Morocco, tends to behave as a metapopulation acting as a whole unit. Due consideration also has to be given to the possible differences in the censusing effort in the two years and the big swings from year to year and even month to month. Thus, in January 2011 5200 Cattle Egrets were counted in the Cáceres catchment area of the Tagus; only a few months earlier, in October 2010, two roosts alone pooled over 3000, this figure falling to 700 in January 2011 and then soaring to no less than 6000 in November 2007. Some districts with heron roosts in autumn were also empty by the following January. Although the information on previous years is bitty, it might well be a habitual practice for the Cáceres catchment area of the Tagus to have a bigger Cattle Egret population in autumn than in winter. What has been clearly recorded is a marked fall in some roosts associated with landfill sites; witness the case of the roost near the capital city of Cáceres capital, which was Spain's biggest in 1992, with nearly 8000 birds; by 2011 the number had dropped to one thousand.
As for the Little Egret, it is difficult to establish a clear trend due to the big difference in the estimated figures for January 1992 (1500 birds) and January 1993 (700). The number of roosts was almost the same 1992 (37) and in 2011 (38) and the number of birds in 2011 (1273) is 15% up on the mean figure for 1992-1993 (1100). Unlike the Cattle Egret, the Little Egret's wintering population has risen sharply in the Tagus catchment area since 1992, with a slight fall in the Guadiana. Another factor that has to be taken into consideration here is the possibility of confusion in some counts with the abundant Cattle Egrets; some small Little Egret roosts might even go totally unnoticed.
According to the annual January Wildfowl Count the trends in Spain (Molina, 2011) for the four heron species are:
- Cattle Egret: reduction in the 1991-2009 period and especially in 2000-2009
- Little Egret: sharp increase from 1991 to 2009, flattening out in 2000-2009
- Grey Heron: increase in the 1991-2009 period
- Great White Heron: sharp increase in the 1991-2009 period.
Lastly, neither in 1992 nor in 1993 were Night Herons or Great White Egrets detected in Extremadura; they would therefore seem to be new winter visitors to the region.
ACKNOWLEDGEMENTS
The National Wintering Heron Count is a project of SEO/BirdLifes' Bird Monitoring Area, run by Juan Carlos del Moral. In Extremadura the survey was coordinated by José María Traverso (Badajoz) and Javier Prieta (Cáceres). The fieldwork involved the collaboration of the 59 following collaborators: Pablo Caballero Javier Prieta, César Clemente, Javier Mahillo, Sergio Mayordomo, Eva Palacios, Jesús Montero, Manuel García del Rey, Emilio Pérez-Balsalobre, Javier Briz, Vicente Risco, Laura Alicia Rodríguez, Carmelo López, Helios Dalmau, Colin Jewitt, Marcelino Cardalliaguet, F. Javier Caballero, José Luis Caballero, Martin Kelsey, Jesús Solana, Juan Carlos Paniagua, Emilio Costillo, Casimiro Corbacho, Fernando Yuste, José Gordillo, Pedro Schreur, Godfried Schreur, Jesús Morena, José Antonio Fimia, Maria Jesús Tarín, Alfredo Mirat, Jesus Rojas, Carmen Galán, Álvaro Martín, Chema Traverso, Álvaro Sánchez Arribas, Antonio Núñez, Diego González Romero, Raquel Rangel Vanessa de Alba, Toribio Álvarez, Celsa Agudo, José María Abad, Patricia Gordon, María Jesús García-Baquero, Manuel Parejo, Raquel García Hierro, J. Elías Rodríguez, Juan Luis Soriano, María Luisa Villoslada, Juan Antonio Barquero, Elvira del Viejo, Juan Villalobos, Antonia Cangas, José Ángel Salas, Gerardo Pizarro, Emilio Jiménez, Agustín Sanabria.
Sources
- Fernández-Cruz, M. & Farinha, J. C. 1992. Primer censo de ardeidas invernantes in la península Ibérica and Baleares (1991-92). Airo 3:41-54. [download PDF]
- Sarasa, C. G., Bartolomé, J., Fernández-Cruz, M. & Farinha, J. C. 1993. Segundo censo de ardeidas invernantes in la penínsulas Ibérica and Baleares (1992-93). Airo 4:41-50. [download PDF]
- Molina, 2011. Censo nacional de aves acuáticas invernantes, Enero 2009. In, Escandell, V.; Palomino, D.; Molina, B.; Leal, A.; Remacha, C.; Bermejo, A.; De la Puente, J. and del Moral, J. C. (Eds.). Programas de seguimiento de SEO/BirdLife in 2009-2010. SEO/BirdLife. Madrid. [download PDF]
Cattle Egret (Bubulcus ibis). Galisteo, Cáceres. Javier PrietaAs already mentioned in this blog, the National Count of Wintering Herons was held last January. As usual the overall result will be published by SEO/BirdLife. For the moment, however, we can give you a foretaste of the Extremadura results.
The chosen methodology was to count birds in communal roosts. The main date was the weekend 15-16 January, although some counts were held a few days later. No information was obtained for the abundant but non-roost-forming Grey Heron. The same goes for the scarcer heron species (Squacco Heron and Bittern) or the ones that are nocturnal or difficult to detect (Little Bittern).
RESULTS BY SPECIESCattle Egret (Bubulcus ibis). 30,917 birds (22,315 in Badajoz and 8602 in Cáceres) in 38 roosts (23 in Badajoz and 15 in Cáceres). Eleven roosts held over one thousand birds, the standout ones being Azud de Badajoz (6103), River Zújar in Villanueva de la Serena (4200), Valuengo Reservoir (2700), Madrigalejo (2400) and River Guadiana in Montijo (2000). The attached map, plotting the location of the roosts, brings out the obvious importance of the River Guadiana and its surrounding meadows, which account for the lion's share of the regional population.
Little Egret (Egretta garzetta). 1273 birds (823 in Badajoz and 450 in Cáceres) in 38 roosts (20 in Badajoz and 18 in Cáceres). Seven roosts held over 50 birds, the biggest being Valuengo Reservoir (230), Madrigalejo (125) and River Guadiana in Montijo (100).
Great White Egret (Egretta alba). 67 birds in 18 roosts (31 in Badajoz and 36 in Cáceres). The biggest roosts were on the River Tiétar in Malpartida de Plasencia (15), Arrocampo Reservoir (9), Valdecaballeros Reservoir(7) and River Zújar in Villanueva de la Serena (6).
Night Heron (Nycticorax nycticorax). 52 birds in 5 roosts, all on the River Guadiana in the province of Badajoz. The most important roosts were Montijo Reservoir in Mérida (29) and Azud de Badajoz (10).
TREND
There's nothing specific to go on in terms of wintering herons in Extremadura. In January 1992 and 1993, however, two Iberian counts were conducted, giving the results by catchment areas (Fernández-Cruz and Farinha, 1992; Sarasa et al., 1993), but without breaking down the figures by regions or provinces. Working from the maps shown in the 1992 count, we estimate about 53,000 Cattle Egrets and 1500 Little Egrets in Extremadura. The 1993 figures were lower but the estimate is rougher because there is no map to go on; maybe the figures were about 42,000 and 700 respectively.
The number of Cattle Egret roosts has fallen from 64 in 1992 to 37 in 2011, a 40% drop. The fall in the number of birds was similar, about 35% on the mean figure for 1992-1993. This decline is much more notable in the Extremadura part of the Tagus catchment area (-60%) than in that of the River Guadiana (-20%). This figures should not really be taken in isolation, however, since the wintering population of the southwest Iberian Peninsula, including Portugal and Morocco, tends to behave as a metapopulation acting as a whole unit. Due consideration also has to be given to the possible differences in the censusing effort in the two years and the big swings from year to year and even month to month. Thus, in January 2011 5200 Cattle Egrets were counted in the Cáceres catchment area of the Tagus; only a few months earlier, in October 2010, two roosts alone pooled over 3000, this figure falling to 700 in January 2011 and then soaring to no less than 6000 in November 2007. Some districts with heron roosts in autumn were also empty by the following January. Although the information on previous years is bitty, it might well be a habitual practice for the Cáceres catchment area of the Tagus to have a bigger Cattle Egret population in autumn than in winter. What has been clearly recorded is a marked fall in some roosts associated with landfill sites; witness the case of the roost near the capital city of Cáceres capital, which was Spain's biggest in 1992, with nearly 8000 birds; by 2011 the number had dropped to one thousand.
As for the Little Egret, it is difficult to establish a clear trend due to the big difference in the estimated figures for January 1992 (1500 birds) and January 1993 (700). The number of roosts was almost the same 1992 (37) and in 2011 (38) and the number of birds in 2011 (1273) is 15% up on the mean figure for 1992-1993 (1100). Unlike the Cattle Egret, the Little Egret's wintering population has risen sharply in the Tagus catchment area since 1992, with a slight fall in the Guadiana. Another factor that has to be taken into consideration here is the possibility of confusion in some counts with the abundant Cattle Egrets; some small Little Egret roosts might even go totally unnoticed.
According to the annual January Wildfowl Count the trends in Spain (Molina, 2011) for the four heron species are:
- Cattle Egret: reduction in the 1991-2009 period and especially in 2000-2009
- Little Egret: sharp increase from 1991 to 2009, flattening out in 2000-2009
- Grey Heron: increase in the 1991-2009 period
- Great White Heron: sharp increase in the 1991-2009 period.
Lastly, neither in 1992 nor in 1993 were Night Herons or Great White Egrets detected in Extremadura; they would therefore seem to be new winter visitors to the region.
ACKNOWLEDGEMENTS
The National Wintering Heron Count is a project of SEO/BirdLifes' Bird Monitoring Area, run by Juan Carlos del Moral. In Extremadura the survey was coordinated by José María Traverso (Badajoz) and Javier Prieta (Cáceres). The fieldwork involved the collaboration of the 59 following collaborators: Pablo Caballero Javier Prieta, César Clemente, Javier Mahillo, Sergio Mayordomo, Eva Palacios, Jesús Montero, Manuel García del Rey, Emilio Pérez-Balsalobre, Javier Briz, Vicente Risco, Laura Alicia Rodríguez, Carmelo López, Helios Dalmau, Colin Jewitt, Marcelino Cardalliaguet, F. Javier Caballero, José Luis Caballero, Martin Kelsey, Jesús Solana, Juan Carlos Paniagua, Emilio Costillo, Casimiro Corbacho, Fernando Yuste, José Gordillo, Pedro Schreur, Godfried Schreur, Jesús Morena, José Antonio Fimia, Maria Jesús Tarín, Alfredo Mirat, Jesus Rojas, Carmen Galán, Álvaro Martín, Chema Traverso, Álvaro Sánchez Arribas, Antonio Núñez, Diego González Romero, Raquel Rangel Vanessa de Alba, Toribio Álvarez, Celsa Agudo, José María Abad, Patricia Gordon, María Jesús García-Baquero, Manuel Parejo, Raquel García Hierro, J. Elías Rodríguez, Juan Luis Soriano, María Luisa Villoslada, Juan Antonio Barquero, Elvira del Viejo, Juan Villalobos, Antonia Cangas, José Ángel Salas, Gerardo Pizarro, Emilio Jiménez, Agustín Sanabria.
Sources
- Fernández-Cruz, M. & Farinha, J. C. 1992. Primer censo de ardeidas invernantes in la península Ibérica and Baleares (1991-92). Airo 3:41-54. [download PDF]
- Sarasa, C. G., Bartolomé, J., Fernández-Cruz, M. & Farinha, J. C. 1993. Segundo censo de ardeidas invernantes in la penínsulas Ibérica and Baleares (1992-93). Airo 4:41-50. [download PDF]
- Molina, 2011. Censo nacional de aves acuáticas invernantes, Enero 2009. In, Escandell, V.; Palomino, D.; Molina, B.; Leal, A.; Remacha, C.; Bermejo, A.; De la Puente, J. and del Moral, J. C. (Eds.). Programas de seguimiento de SEO/BirdLife in 2009-2010. SEO/BirdLife. Madrid. [download PDF]
No comments:
Post a Comment