Michael Viney responds to queries and observations on nature.
We feed the birds in our garden. My grandfather in Ballsbridge, Dublin, also feeds the birds. We have noticed that the blue tits in Ballsbridge are quite spherical compared with ours. This is not just fluffed out in cold weather, they are like this in warm weather. Are there subspecies, or are birds in Dublin so well fed that they are obese?
... Michael Towers, Navan, Co Meath
The body weight of blue tits, according to research carried out in Sweden, is mainly hereditary, a result of the genes in a particular population. The Co Meath birds should interbreed with the Ballsbridge birds to increase their weight.
Crossing O'Connell Street Bridge, I spotted an otter disappearing down the steps into the Liffey. I waited to see if it would surface, and spotted a cormorant and a heron. Unfortunately, I didn't see the otter again.
... Philip Duggan, TCD, Dublin
I saw a blackbird with a white neck and a yellow beak. Was this strange?
... Niall Finnerty, Ballina, Co Mayo
It was partially albino. The feathers turn white because of injury or poor food.