Hi All,

 

Rob Thorn noted in his post about the "Gahanna Waxwings" that waxwings have seemed few and far between this spring.

 

I've actually noticed the same thing, but have also noticed that we don't seem to have the cottonwood "fluff" floating around like we've had in previous years around this time.  In the last couple of years at least, we've had cottonwood seeds drifting along on the wind like snowflakes by the weekend of International Migratory Bird Day.

 

I mention the lack of cottonwood seeds because it suggests that cottonwoods in the state may have experienced some problems as a result of the late cold snap, and this may potentially affect waxwings.

 

There are a number of different kinds of fruits that many birds don't eat until spring.  The fruits remain on the trees and bushes throughout the winter.  Many of these fruits possess secondary chemical compounds in them that protect them against seed predators, like squirrels and chipmunks, and reduce bacterial activity to prevent them from rotting.  These secondary chemical compounds make them distasteful, at the very least, and in some cases toxic.  An example of one of these kinds of plants is American Cranberrybush (Viburnum opulus).  American Cranberrybush berries contain secondary compounds that make the fruit very acidic.  When eaten, the acid content of the fruit can potentially affect the acid/base balance in a bird's body.  To counter the acid in the fruit, waxwings have to use protein (which is made up of nitrogen) from their own bodies to make a buffer to the acid of the berries, unless they can find another source of nitrogen.  The pollen of cottonwood catkins contains nitrogen, and provides waxwings with an alternative source to use to counter the acid of the berries.

 

A researcher figured out that waxwings don't eat American Cranberrybush berries until the male catkins of Eastern Cottonwoods become available in the spring.  Then the waxwings eat both the berries and the catkins, which helps them deal with the acid compounds.

 

This is an example of dietary complementation, and is only the tip of the iceberg of our understanding of these kinds of relationships.

 

If cottonwoods took a hit as a result of the late cold snap, it may mean that waxwings have not been able to utilize the late season fruits as effectively as they normally would and have had to disperse a little more widely to find other kinds of fruits to eat.  If there are other plants that contribute to a bird's dietary complementation who knows how this spring has affected those relationships as well.

 

Couple this idea with the fact that we experienced high fruit abcission during the winter in some parts of the state which may mean that food availability may be down this season.  This may in turn affect productivity and survivorship for many birds in the state.  This is only a guess, and only time and thorough research and observations will actually be able to tell us what this late cold snap will mean for birds in Ohio.

 

I should mention that it may not just be the late cold snap that's affected things.  It seems like it's also been relatively dry these past several weeks, which may have affected plants like cottonwoods as well.  Weather forecasters are predicting thunderstorms tonight for parts of the state so it will be interesting to see if the rain helps at all.

 

Just something to think about,

 

Casey Tucker

Columbus, OH