My previous post started off the list of species that can be found on the lake at Whiteknights Campus. Here is a brief description of some of the species within the family Anatidae that I saw during my surveys:
Mute Swan (Cygnus olor)
The Mute Swan is one of the largest birds in Britain, with a wingspan of over 2 metres (BBC, 2012), and also one of the largest herbivorous water birds (Gayet et al, 2011). Both parts of the scientific name ‘Cygnus olor’ translate to ‘swan’ in latin (BTO, 2012).
In England, Swan Upping was a tradition where swans on the River Thames were marked for the Crown due to their popularity as a food source. Today, Swan Upping is a yearly census and health assessment of the Mute Swan population along sections of the river (The Royal Household, 2012).
Due to their increase in numbers across Western Europe in recent years, research has been carried out to assess the possible impacts these large grazing birds may have on ecosystems they inhabit. One such study has found evidence to suggest that an abundance of Mute Swans negatively impacts the presence, abundance and diversity of macrophytes; aquatic plants which are important for oxygenation of the water, nutrient cycling, and for providing cover for fish and invertebrates (Gayet et al., 2012).
Canada Goose (Branta canadensis)
Native to North America, the Canada Goose was imported into the UK in the 17th Century by King Charles II to be part of the Royal collection (ISSG, 2010). Inevitably, individuals escaped from such collections, and in 2000 the Canada goose population was estimated at over 88,000 adults (Baillie et al., 2010). However, these large birds tend to form sprawling flocks, which produce such a substantial amount of droppings that the increased nutrient levels can lead to algal blooms in water bodies. These large flocks also tend to trample the ground as they graze, leading to compacted earth known as a ‘hard pan’, and preventing new plant growth; sometimes causing a dramatic change to the habitat (ISSG, 2010).
For many reasons, including those mentioned, Canada Geese are often seen as a ‘pest’ species and claims that they harbour pathogenic bacteria has given them a poor reputation. Despite this, these birds are a familiar urban sight and are regularly fed by the general public. I, for one, still maintain a fondness for these highly social and successful geese.
Mallard (Anas platyrhyncos)
At this time of year, you can see Mallards finding mates and pairing off together, but it is not until March that they will begin to create a nest. Males, known as Drakes, often outnumber the females and the rejected males will sometimes mob a female and force copulation; a behaviour seen often in the Anatidae family (Burns et al, 1980).
Males that have managed to find a mate will stay with their female until after the eggs have been laid, and gradually lose interest. The males then gather into groups in order to moult (RSPB, 2012).
Mallards often interbreed with other members of the genus Anas, and domesticated ducks that have Mallard ancestry often escape and breed with their wild counterparts. Examples of this can be seen on the lake.
Although it is not necessarily an issue in areas of flowing water, frequent provision of extra food sources for Mallards may not be beneficial. An increase in the population due to increased food provision can be hazardous to nesting females, who may be harassed when foraging by unattached males, and a large residential population can lead to increased dropping, which in turn leads to higher algae growth; stunting aquatic plant growth and depriving the water of oxygen, which could lead to botulism during periods of hot weather. Botulism is a large problem in water bodies, and kills millions of water birds around the world each year (RSPB, 2012).
Mandarin (Aix galericulata)
Mandarins used to be thought of as monogamous in Japan, and pairs were often given as presents to newly-weds as a symbol of fidelity (WWT, 2012). These were introduced from China to the UK, in fact the first record of the Mandarin in Britain was in Berkshire in 1866 (The Cornell Lab of Ornithology, 2012). Initially kept as ornamental birds, the wild population in Britain is due to escapees and there are now approximately 7000 feral birds in the UK (WWT, 2012).
In the Far East, this bird is now in decline due to the destruction of their natural habitat, however they are still listed as ‘Least Concern’ on the IUCN Red List due to their large range and stable populations in some areas (BTO, 2012).
There is a fairly small but conspicuous group that reside on the campus lake, which tend to be much more shy than the Mallard but can be tempted to come very close with the offering of food. During the courtship period, these are very entertaining ducks to watch and make a range of distinctive noises which differ between sexes. They also have some interesting nesting behaviour, similar to that of the Wood Duck (below).
Wood Duck (Aix sponsa)
The Wood Duck (Aix sponsa – meaning ‘water bird in a bridal dress’) is Native to North America, and similarly to the Mandarin, was imported as an ornamental bird into the UK (NPWRC, 2006).
In the picture below, you can see that male Wood Ducks will often court female Mandarins, and vice versa. However, chromosomal differences between the species make hybrids very rare, and it is thought that if any arose they would be sterile (Johnsgard, 1960).
Unusually for ducks, the Wood Duck nests in holes in trees which have been created by other species, and has clawed feet to allow them to perch in branches. The newly hatched ducklings must jump to ground before travelling to water, which may seem like a daunting drop, but their small size ensures they do not suffer any damage. Some Wood Ducks will produce two clutches per season, and if suitable nesting areas are few or close together, females may lay eggs in other nests; known as ‘egg dumping’ or intraspecific brood parasitism (Cornell Lab of Ornithology, 2012).
To be continued…
Baillie, S.R., Marchant, J.H., Leech, D.I., Renwick, A.R., Joys, A.C., Noble, D.G., Barimore, C., Conway, G.J., Downie, I.S., Risely, K. & Robinson, R.A. (2010). Breeding Birds in the Wider Countryside: their conservation status 2010. BTO Research Report No. 565. BTO, Thetford.
Burns, J. T., Cheng, K. M., and McKinney, F. (1980) Forced Copulation in Captive Mallards 1. Fertilization of Eggs. The Auk. 97(4). 875-879.
BTO (2012) Mandarin Duck Aix galericulata URL: http://www.birdlife.org/datazone/speciesfactsheet.php?id=418 [03/11/12]
The Cornell Lab of Ornithology (2012) Wood Duck URL: http://www.allaboutbirds.org/guide/Wood_Duck/id [08/11/12]
The Cornell Lab of Ornithology (2012) Wood Duck Life History URL: http://www.allaboutbirds.org/guide/Wood_Duck/lifehistory [08/11/12]
Gayet, G. et al. (2011) Do mute swan (Cygnus olor) grazing, swan residence and fishpond nutrient availability interactively control macrophyte communities? Aquatic Botany. 95. 110-116.
ISSG (2010) Branta canadensis (bird) URL: http://www.issg.org/database/species/ecology.asp?si=1427&fr=1&sts=&lang=EN [07/11/12]
Johnsgard, P. A. (1960) Hybridization in Anatidae and its Taxonomic Implications . The Condor. 62. 25-33.
NPWRC (2006) Wood Duck (Aix sponsa) URL: http://www.npwrc.usgs.gov/resource/birds/woodduck/ [08/11/12]
The Royal Household (2012) Swan Upping URL: http://www.royal.gov.uk/royaleventsandceremonies/swanupping/swanupping.aspx [05/11/12]
RSPB (2012) Breeding URL: http://www.rspb.org.uk/wildlife/birdguide/name/m/mallard/breeding.aspx [05/11/12]
RSPB (2012) Mallard Overpopulation URL: http://www.rspb.org.uk/wildlife/birdguide/name/m/mallard/overpopulation.aspx [05/11/2012]
WWT (2012) Mandarin URL: http://www.wwt.org.uk/learn/fact-files/wetland-wildlife/species-fact-files/mandarin-duck [03/11/12]