Their protein intake during winter and into spring will directly impact on the breeding performance of your garden birds. Birds with higher fat content tend to breed earlier and often have larger broods. The bone meal garden bird booster will attract some of the more illusive bird species to the bird tray such as, shrikes, starlings, flycatchers, hoopoes, woodpeckers, thrushes, robins and bulbul. All of our Garden Bird Boosters contain added trace elements, vitamins and minerals.