The lack of protection from cold, ice and snow may increase deaths among species using white pine. Limiting factors affect birth rates or death rates, or both, and so affect the population of a species in that habitat. Environmental constraints, or decimating factors, include predation by wild animals, disease, weather, hunting and trapping. In habitats of high quality, the effects of decimating factors may be alleviated and populations can usually rebound. The drought last summer and the ice storm of recent memory are two good examples of decimating factors.
Some species produce more offspring than others.
Each species has a maximum genetic reproductive potential, also called biotic potential. In general, species at the higher end of the food chain have fewer offspring and species at the lower end have more offspring. A broad-winged hawk, a predator fairly high in the food chain, usually has two or three young each year. Shrews are a staple of their diet, and the northern short-tailed shrew has two or three litters a year, with about five young in each litter. So the biotic potential of this shrew is higher than that of the broad-winged hawk.