AT times it seems as though the Yorkshire landscape is becoming overwhelmed by alien wildlife with moors and reservoirs increasingly dominated by descendants of introduced Canada geese and feral greylags. River banks have native plants crowded out by Himalayan balsam while seeds falling from feeders in gardens tend to be mopped up by grey squirrels and pheasants.

The one introduced species I am always pleased to see is the Mandarin Duck, first imported into this country around 1745 although a free-flying population only established itself in the 20th century.

Their British numbers of about 2300 pairs constitute at least 10% of the world total for in their native habitats in Japan, China and Siberia they are declining due to destruction of their forest habitat and overhunting.

They were originally concentrated in the south of England but spread north until now they are well established along the Wharfe and the Washburn, spreading out from their stronghold in the woods below Bolton Abbey (pictured: a male in a Strid Wood tree) where their winter numbers can peak at up to 60, attracted by fallen beechmast and acorns.

A reliable spot to see them is Adel Dam where a hide overlooks a quiet pool ringed by woodland.

Until a few years ago the ponds in our garden, backing onto Farnley Hall Woods, also functioned as woodland pools until first, most of the large, marketable timber was felled. More recently, a wide swathe of trees was removed to allow construction of a ditch to stop flooding from a small stream that at times inundated gardens lower down the hill.

Our back garden has therefore opened up and it is now six years since our last visit from a mandarin. In 2014 a female had spent a while around our biggest pond before flying off into the adjoining woods where I hoped she might have a nest in a tree cavity. In 2016 a pair arrived and mated on the water of the same pond. They flew off towards the river and we did not see them again.

Locally their numbers have certainly increased and up to four could be seen last autumn perched along the top of the weir in Wharfemeadows Park among the bigger mallards.

As to our garden, in the absence of mandarins we are hoping for the return of the female mallard which nested on the bank of one of the ponds last year. While not as beautiful or exotic as a mandarin she was very welcome.

wharfedale-nats.org.uk