Pochard: a bird population in decline

TafelenteThe fate of the Common Pochard is discussed intensively in the relevant forums. Scientific research suggests that the sex ratio of the populations of Common Pochard (Aythya ferina), a medium-sized diving duck, in Europe and North Africa has changed. This could play a role in the decline of the species in the Western Palearctic.

Sex ratio results have just been published in the Wildfowl & Wetlands Trust (WWT) Journal Wildfowl. These conclusions show that populations are becoming increasingly “masculine”. Using the data obtained in January 2016, the researchers compared counts from surveys conducted in January 1989 and January 1990 in the same region. The proportion of men in the total population was 62% in the years 1989 to 1990 and in 2016 this disparity even increased to 71%.

Interesting clues for the pochard, a bird in a sharp population descent, provides an investigation of ZIMMERMANN, H. (2010), which was published in: Brut und Mauser der Tafelente Aythya ferina im Naturschutzgebiet Fischteiche in der Lewitz (Breeding and moulting of the pochard Aythya ferina in the nature reserve fish ponds in the Lewitz) in Orn. Newsletter Meckl.-Vorp. 46: 367-373.

The fish ponds in the Lewitz are a traditional breeding and moulting area of the Common Pochard in Mecklenburg-Vorpommern in north-eastern Germany. The highest count with 200 breeding pairs and more was found in the period between 1970 and 1981. Since the late 1980s, the number of breeding pairs has fallen dramatically and is currently tending towards zero.

Since the beginning of the 1990s, significant declines have been recorded in the entire range of the Common Pochard. And this is especially true for an old stronghold of the species, eastern Germany. The factors of decline cannot be determined in general with certainty. But the Lewitz Fischteiche had several area-specific factors that might highlight some reasons.

In the late 1960s, the intensification of carp (Cyprinus carpio) production started. Due to pond maintenance, fertilization and increased feeding, the fish yield per hectare increased from originally about 150 kg to a maximum of 1,000 kg. The result was a nutrient enrichment in the ponds. The Pochards benefited from the proven direct uptake of carp feed as well as from the eutrophication in the ponds, which resulted in lush growth of floating leaf and underwater plants. In large populations, Pondweed (Potamogeton sp.), Hornwort (Ceratium sp.), Common Waterweed (Elodea sp.) and Water Knotweed (Polygonum amphibium). These plant species, particulary their seeds and plant parts predominate in the vegetable diet portion of the pochard according to BAUER, K.M. & GLUTZ VON BLOTZHEIM, U.N.

in his “Handbuch der Vögel Mitteleuropas”, Band 3. Anseriformes (2. Teil) (1980). Eutrophication was further enhanced by the production of ducks for fattening on the ponds, which began in 1963, and was increased to 800 t / year by the end of the 1980s. For the protection of the mast ducks intensive trapping and shooting of predatory mammals took place during the entire year.

Due to the intense predatory control and the fact that the invasive species Raccoon (Procyon lotor), Raccoon Dog (Nyctereutes procyonoides) and Mink (Mustela vison) were not common at that time, predation played a minor role. The situation in the pond economy changed radically from 1979 onwards. From 1979 to 1989 all pond groups but one were reconstructed in such a way that several ponds were collapsed and the dams increased. In addition, the pond depths were increased and the reeds were eliminated up to 80%. The consequence was the decline of the pochard breeding stock to less than 100 BP. Towards the end of the reconstruction period from 1987, the stock increased again, but then gradually began to decline after 1991.

 

All the factors that previously favored the pochards ceased to exist. After privatization, the fishery underwent a significant extensification and the fattening of the ducks was completely discontinued. The fishery was authorized to shoot Cormorants (Phalacrocorax carbo) without restriction on all the spearfish ponds, causing a great deal of concern. Premium payments for the catching or shooting of predatory mammals were no longer made and the Neozoa Raccoon, Raccoon Dog and Mink spread all over the area. The influence of the predatory mammals on the broodstock development not only of the pochard, but for almost all waterbird species increased even further, because from 2003 to 2009 predator control was completely omitted. Since 2003, studies of the Technical University of Dresden have been conducted in the pond area on alien and native predatory mammals and their influence on waterfowl. The task includes u. a. also the regular search and control of waterfowl nests. This should have added to disturbance in the area.

 

Since the beginning of the striking resting concentrations in the mid-1960s, it can be assumed that the high numbers present on the sites are not on migration but moulting. The Brood- moulting starts with the male pochards at the beginning of June. At this time, in which the first young hatch, most of the drakes already leave the breeding areas and gather in suitable places. In the Lewitz this is the case regularly. In the years 1968 to 1983 a maximum of up to 4,500 individuals were present in June. The total numbers were determined by ornithologists as accurately as possible each year; However, the determination of the sex relationship was omitted. From the beginning, however, the drakes outweighed the females in numbers in June.

 

These statements show that there may also be natural reasons for a mismatch between females and males. Nevertheless, it seems obvious that one factor in particular has a negative influence on the survival rate of females compared to males. Predation by a number of introduced non-native mammals poses a major threat to native brood population. This is certainly a major reason which explains the increased mortality. The females are simply more exposed during the breeding season. They spend more time at the breeding grounds, hatching eggs and raising the ducklings.

 

Tag: Raccoon, Procyon lotor, Raccoon Dog, Nyctereutes procyonoides, Mink, Mustela vison, Cormorant, Phalacrocorax carbo, Common Pochard, Aythya ferina, Wildfowl & Wetlands Trust, WWT, ZIMMERMANN, H. (2010), Brut und Mauser der Tafelente Aythya ferina im Naturschutzgebiet Fischteiche in der Lewitz, Orn. Rundbrief Meckl.-Vorp., BAUER, K.M. & GLUTZ VON BLOTZHEIM, U.N., Handbuch der Vögel Mitteleuropas

Pochard: a bird population in decline

 

The fate of the Common Pochard is discussed intensively in the relevant forums. Scientific research suggests that the sex ratio of the populations of Common Pochard (Aythya ferina), a medium-sized diving duck, in Europe and North Africa has changed. This could play a role in the decline of the species in the Western Palearctic.

 

Sex ratio results have just been published in the Wildfowl & Wetlands Trust (WWT) Journal Wildfowl. These conclusions show that populations are becoming increasingly “masculine”. Using the data obtained in January 2016, the researchers compared counts from surveys conducted in January 1989 and January 1990 in the same region. The proportion of men in the total population was 62% in the years 1989 to 1990 and in 2016 this disparity even increased to 71%.

 

Interesting clues for the pochard, a bird in a sharp population descent, provides an investigation of ZIMMERMANN, H. (2010), which was published in: Brut und Mauser der Tafelente Aythya ferina im Naturschutzgebiet Fischteiche in der Lewitz (Breeding and moulting of the pochard Aythya ferina in the nature reserve fish ponds in the Lewitz) in Orn. Newsletter Meckl.-Vorp. 46: 367-373.

The fish ponds in the Lewitz are a traditional breeding and moulting area of the Common Pochard in Mecklenburg-Vorpommern in north-eastern Germany. The highest count with 200 breeding pairs and more was found in the period between 1970 and 1981. Since the late 1980s, the number of breeding pairs has fallen dramatically and is currently tending towards zero.

Since the beginning of the 1990s, significant declines have been recorded in the entire range of the ommon Pochard. But this is especially true for an old stronghold of the species, eastern Germany. The factors of decline cannot be determined in general with certainty. But the Lewitz Fischteiche had several area-specific factors that might highlight some reasons.

In the late 1960s, the intensification of carp (Cyprinus carpio) production started. Due to pond maintenance, fertilization and increased feeding, the fish yield per hectare increased from originally about 150 kg to a maximum of 1,000 kg. The result was a nutrient enrichment in the ponds. The Pochards benefited from the proven direct uptake of carp feed as well as from the eutrophication in the ponds, which resulted in lush growth of floating leaf and underwater plants. In large populations, Pondweed (Potamogeton sp.), Hornwort (Ceratium sp.), Common Waterweed (Elodea sp.) and Water Knotweed (Polygonum amphibium). These plant species, particulary their seeds and plant parts predominate in the vegetable diet portion of the pochard according to BAUER, K.M. & GLUTZ VON BLOTZHEIM, U.N.

in his “Handbuch der Vögel Mitteleuropas”, Band 3. Anseriformes (2. Teil) (1980). Eutrophication was further enhanced by the production of ducks for fattening on the ponds, which began in 1963, and was increased to 800 t / year by the end of the 1980s. For the protection of the mast ducks intensive trapping and shooting of predatory mammals took place during the entire year.

Due to the intense predatory control and the fact that the invasive species Raccoon (Procyon lotor), Raccoon Dog (Nyctereutes procyonoides) and Mink (Mustela vison) were not common at that time, predation played a minor role. The situation in the pond economy changed radically from 1979 onwards. From 1979 to 1989 all pond groups but one were reconstructed in such a way that several ponds were collapsed and the dams increased. In addition, the pond depths were increased and the reeds were eliminated up to 80%. The consequence was the decline of the pochard breeding stock to less than 100 BP. Towards the end of the reconstruction period from 1987, the stock increased again, but then gradually began to decline after 1991.

All the factors that previously favored the pochards ceased to exist. After privatization, the fishery underwent a significant extensification and the fattening of the ducks was completely discontinued. The fishery was authorized to shoot Cormorants (Phalacrocorax carbo) without restriction on all the spearfish ponds, causing a great deal of concern. Premium payments for the catching or shooting of predatory mammals were no longer made and the Neozoa Raccoon, Raccoon Dog and Mink spread all over the area. The influence of the predatory mammals on the broodstock development not only of the pochard, but for almost all waterbird species increased even further, because from 2003 to 2009 predator control was completely omitted. Since 2003, studies of the Technical University of Dresden have been conducted in the pond area on alien and native predatory mammals and their influence on waterfowl. The task includes u. a. also the regular search and control of waterfowl nests. This should have added to disturbance in the area.

Since the beginning of the striking resting concentrations in the mid-1960s, it can be assumed that the high numbers present on the sites are not on migration but moulting. The Brood- moulting starts with the male pochards at the beginning of June. At this time, in which the first young hatch, most of the drakes already leave the breeding areas and gather in suitable places. In the Lewitz this is the case regularly. In the years 1968 to 1983 a maximum of up to 4,500 individuals were present in June. The total numbers were determined by ornithologists as accurately as possible each year; However, the determination of the sex relationship was omitted. From the beginning, however, the drakes outweighed the females in numbers in June.

These statements show that there may also be natural reasons for a mismatch between females and males. Nevertheless, it seems obvious that one factor in particular has a negative influence on the survival rate of females compared to males. Predation by a number of introduced non-native mammals poses a major threat to native brood population. This is certainly a major reason which explains the increased mortality. The females are simply more exposed during the breeding season. They spend more time at the breeding grounds, hatching eggs and raising the ducklings.

To cope with the growing demand for top shots of the rarer species of the Palearctic Bird-Lens is keen to enrich the range of pictures of birds you can find in the western palearctic. Trips to remote places to capture images of rare birds of western palearctic were very successful. Beside the image above you can find a nice selection of birds in the “Picture Shop” very soon. Just give a message, if Bird-Lens could serve you with an image needed before the new pictures are online.

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