Natural food sources in our landscapes are scarce at this time of year, so feed the birds with suet cakes and birdseed to provide protein and fat. If squirrels are monopolizing your bird feeder, consider adding a baffle, using safflower seed or switching to a squirrel resistant feeder.
If you have a bird bath in your garden, be sure to use a de-icer to prevent the water from freezing.
Protect your landscape from hungry deer. Repellents produce strong scents and some are combined with a nasty taste to deter deer from browsing in your garden. Continue to apply them on a regular basis as feeding pressure often increases in the winter.