I like cake. My favorites are Boston cream pie, tiramisu, and that yummy fruit and cream cake my mom used to get for my birthday. These cakes are pretty different, but what they do have in common are layers. Each cake is unique and its individual layers make the cake delicious and complete.
Now that you’re salivating for some sugary goodness, I’m going to throw you for a loop. Birds like cake too, and I’m not talking about those gulls that harass your beach spot. For the birds I’m thinking about, their cake is the forest. From a distance, the forest looks like one continuous green wall. If you look carefully, you will see different types of trees and shrubs that make the wall complete. Each layer is unique, providing something critical for a species’ survival. Some birds need multiple layers for survival like the prairie warbler. Found in scrubby fields, young forests, and even some mature forests to sing, feed, and use for shelter, they will only nest in trees less than 10 feet high. Others, like the blackburnian warbler, breed, nest and feed in the highest peaks of conifer forests.
Some birds even have a preference for a forest layer based on their sex. When Bicknell’s thrush head south to the Caribbean for the winter, the males and females split up. Male Bicknell’s thrush are found in more pristine, higher-elevation tropical-moist forests. Females are found at lower elevation wetter forests. So this bird species needs both habitat types to survive.
Let’s get back to that cake. Unlike me, birds are pickier about their cake and don’t easily move on to the next layer. Impacts to any one of the forest layers will have consequences for the species that depend on it. What would the blackburnian warbler do if that top layer of its forest cake was gone? And where would the prairie warbler raise its young if the understory layer was missing? And if there is not enough low elevation forest for female Bicknell’s thrush to feed in, they will not survive to make the journey north to breed.
The forests we are familiar with are changing. Forestry practices, changes in land use and development all affect the health of the forest system. These changes can effect the structure of the layers and overall size of the forest, which can benefit some birds but is a harmful to others (many of which are of conservation concern).
A cake can become dry and burned if the temperature is too high, and so can a forest. The conifer forests that many of our highest priority species live in won’t thrive in a warmer environment; and the food and shelter they provide will no longer be available. And a warmer climate increases the risk of drought and fire (Find more: http://www.epa.gov/climatechange/impacts-adaptation/forests.html).
In my life, cake is pretty important. At the end of the day though, I can (and probably should) live without it. For birds, their layered cake—the forest—is essential, with each layer critical to their survival.