Species up­date

Milder win­ters have proved ben­e­fi­cial to the Mute Swan pop­u­la­tion, says Kate Risely

Bird Watching (UK) - - Contents - Kate Risely is the Bri­tish Trust for Or­nithol­ogy’s Gar­den Bird­watch Or­gan­iser

MUTE SWANS ARE a fa­mil­iar and mostly peace­ful pres­ence on nearly all of our lakes and wa­ter­ways, even in busy towns, a ha­bit­u­a­tion born of hun­dreds of years of semi-do­mes­ti­ca­tion. Un­der ex­ten­sive and tightly-con­trolled sys­tems of own­er­ship dat­ing back to at least the 15th Cen­tury, and likely long be­fore, wild birds were rounded up, marked, had their wing tips cut off, and were con­trolled as a re­source for the ta­ble. The right to the lo­cal swans was a priv­i­lege be­stowed by the crown on nobles, wealthy landown­ers and the clergy, with se­vere penal­ties for poach­ers. One rem­nant of this prac­tice is the tra­di­tional ac­tiv­ity of ‘swan up­ping’, in which the Mute Swans on one sec­tion of the Thames are rounded up each year and marked by the Vint­ners and Dy­ers liv­ery com­pa­nies, de­scen­dants of me­dieval trade guilds. To­day, the up­ping is cer­e­mo­nial; birds are marked with rings, rather than bill nicks, and are counted and checked for en­tan­gled fish­ing tackle, rather than taken to eat. An­other echo of this long cul­tural tra­di­tion can be found in the wide­spread, yet hazy, be­lief that swans are spe­cially pro­tected be­cause they be­long to the Queen. While there is a royal pre­rog­a­tive, this does not trans­late to any prac­ti­cal ad­di­tional pro­tec­tion for to­day’s Mute Swans, above that ac­corded to most wild birds. This man­age­ment of Mute Swans con­tin­ued in ar­eas such as the fens un­til the end of the 18th Cen­tury, and our cur­rent pop­u­la­tion is mainly de­scended from these semi-do­mes­ti­cated an­ces­tors. His­tor­i­cal records in­di­cate that in the 16th Cen­tury there were an es­ti­mated 24,000 Mute Swans in the fens alone, a tes­ta­ment to the ex­ten­sive rivers and wet­lands that were once found in Bri­tain, as well as pro­tec­tion. The first Bri­tish Mute Swan Cen­sus was or­gan­ised by the BTO in 1955, and re­sulted in a na­tional pop­u­la­tion es­ti­mate of about 20,000 birds. Since then, sur­veys and cen­suses or­gan­ised by the BTO and the Wild­fowl and Wet­lands Trust re­vealed a gen­eral in­crease in num­bers between the 1960s and the 1980s, and, to­day, there are thought to be about 30,000 in­di­vid­ual Mute Swans in the UK, although the large pro­por­tion of non­breed­ers means that this only in­cludes about 6,000 breed­ing pairs. The pop­u­la­tion in­crease in re­cent years is thought to be partly due to the re­duc­tion of lead poi­son­ing. Mute Swans mainly feed on pondweed, and they swal­low grit to help them grind down veg­e­ta­tion. This habit means they are vul­ner­a­ble to poi­son­ing from dis­carded an­glers’ weights and spent gun­shot. This was a ma­jor cause of mor­tal­ity in the 1970s, but for­tu­nately a sub­se­quent ban on lead weights for fish­ing has re­duced, if not elim­i­nated, swan deaths through lead poi­son­ing. Un­like other swans, our Mute Swans are very seden­tary, and don’t gen­er­ally move far between the win­ter and breed­ing sea­sons. How­ever, they suf­fer in freez­ing con­di­tions, and are more likely to move long dis­tances in search of open wa­ter. There have been rel­a­tively few records of ringed birds mov­ing over­seas, and the fur­thest recorded jour­ney was by a bird that was ringed in Lithua­nia, and re­cov­ered in Scot­land in Jan­uary 1959. Gen­er­ally, milder win­ters ap­pear to be ben­e­fit­ing this species, and their thriv­ing pop­u­la­tion has also been at­trib­uted to an in­creas­ing re­liance on gravel pits and ponds, and also to im­prove­ments in our wa­ter qual­ity..

Un­like other swans, our Mute Swans are very seden­tary, and don’t gen­er­ally move far between the win­ter and breed­ing sea­sons

FA­MIL­IAR SIGHT Mute Swans can be seen on most lakes and wa­ter­ways

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