WB#4: Tufted Duck
The cache, a small, black-taped plastic jar is hidden at the top of the river bank adjacent to the busy main road. It is at the end of this short trail where Mickle Ing Beck enters the Wharfe and from where a pair of these attractive ducks could be seen on the mid-river pebbles a little upstream which are exposed during low water flows.
To reach the cache location: a) if continuing in a sequence from WB#1 and WB#2: park in the visitor car park @ N 53 54.212 W 1 42.471 and head west along the riverside trail to the cache location.
b) if doing WB#3 and WB#4 separately: park @ N 53 54.227 W 1 42.741 at the end of the old Ilkley Rd and make your way down to and along the small riverside trail to the cache location.
The tufted duck (Aythya fuligula) is a small diving duck found in northern Eurasia. Its scientific name is derived from Ancient Greek aithuia an unidentified seabird mentioned by authors including Hesychius and Aristotle, and Latin, fuligo 'soot' and gula 'throat'.
The unmistakeable adult male is all black except for white flanks and a blue-grey bill with gold-yellow eyes, along with a thin crest on the back of its head. It has an obvious head tuft that gives the species its name.
The adult female is brown with paler flanks, and is more easily confused with other diving ducks. In particular, some have white around the bill base which resembles the scaup species, although the white is never as extensive as in those ducks. In flight it shows an obvious white stripe across the back of the wing.
It is 40-47cm long with a wingspan of 67-73cm and weighs 450-1,000g. It has an average lifespan of 4 years.
The females' call is a harsh, growling 'karr', mostly given in flight (listen here). The males are mostly silent but they make whistles during courtship based on a simple 'wit-oo'.
It breeds in the UK across lowland areas of England, Scotland and Ireland, but less commonly in Wales, with 
most birds being residents. Numbers increase in the UK in winter because of birds moving to the UK from Iceland and northern Europe.
It is believed to have expanded its traditional range with the increased availability of open water due to gravel extraction, and the spread of freshwater mussels, a favourite food.
They ducks are migratory in most of their range, and overwinter in the milder south and west of Europe, southern Asia and all year in most of the United Kingdom. One individual has been reported as far south as Melbourne, Australia. They form large flocks on open water in winter.
Their breeding habitat is close to marshes and lakes with plenty of vegetation to conceal the nest. They are also found on coastal lagoons, shorelines and sheltered ponds - and along certain stretches of the River Wharfe - as here!
They birds feed mainly by diving, but they will sometimes upend from the surface. They eat molluscs, aquatic insects and some plants and sometimes feed at night.
See here for a video of a female with her ducklings, here for a family busy preening on the nest, here for a fascinating underwater video of tufted ducks, mallard and swan feeding