Are tennis balls toxic

We have installed a bird feeder in our garden, hoping to attract small birds. A flock of ravens sit in a nearby lime tree, descending on the feeder so that not a single small bird dares to feed from it. How can we prevent the ravens from dominating the feeder? AT, by email

Special feeders enclosed in cages (as sold to exclude squirrels) are the best way of deterring larger birds. Many bird-feeders are designed to have cages retrofitted if required, so you may be able to buy just a cage rather than a new feeder.

You can also influence the type of visiting birds by choosing bird food that’s appropriate for the type that you want to attract. For smaller birds, make sure that you leave out the sort of energy-rich food that they enjoy and need.

A mix containing a high proportion of “sunflower hearts” is the best choice and black sunflower seeds are another option. Don’t use mixes that contain lots of cereals or items such as dried peas or bits of broken dog biscuit. These will be less attractive to tits and finches, but they’re just the sort of thing that larger birds are looking for, so if there’s any spillage, you’ll attract the wrong type of bird.

Visit to see an excellent range of feeders and wild bird foods.

My seven-year-old Border collie had a suspected reaction to his vaccine last year. He was very quiet on the journey home and after getting out of the car he had difficulty using his back legs.

I took him back to the vet and he made a full recovery within 24 hours. He has had regular boosters previously with no reaction. I am now worried about what to do this year. Does he still need boosters, or has he built up enough immunity? ET, by email

A classic allergic reaction to a vaccine would have involved signs such as facial swelling, skin eruptions, vomiting or fainting, rather than the vague weakness that you describe. Still, it would be sensible to be cautious about giving exactly the same injection again.

In Britain, the essential vaccines are distemper, hepatitis, parvovirus and leptospirosis. After seven years of regular vaccines, your dog should have long-term protection against the first three diseases without further boosters. A new lab test, the Canine VacciCheck, measures antibody levels and might help to reassure you that he is definitely protected against these viruses (watch ).

The vaccine against the fourth disease – leptospirosis – definitely only lasts for one year. To protect against this, a single agent lepto-only booster vaccine could be given, perhaps using a different brand, and pre-treating with antihistamines to minimise the risk of another reaction. Talk to your vet about this.

I am desperate to find a way of stopping my cat killing so much wildlife. This has become a real problem between me and the neighbours. I hate the killing too, and am at the end of my tether. Apart from keeping him in as a house cat, do you have any suggestions? SE, by email

The CatBib is a new idea that has been developed by a cat lover who could no longer stand the fact that her cats regularly hunted birds.