The American redstart (Setophagaruticilla) is in serious decline. Scientists have been able to correlate health and breeding success to levels of 13C in their blood (a chemical signature indicating the source of their diet). Birds with lower levels of 13C in their blood return to their spring breeding ground sooner, weigh more and produce more offspring. Based on this, what would you expect to find in the wintering grounds of the American redstart? Check all that apply.

Question

_____  Limited availability of habitat in areas where plants have low13C.
_____  Higher insect biomass in areas where plants have low13C.
_____  A lack of territorial behavior being displayed by American redstarts.
_____  Differences in food quality correlating with levels of 13C in the habitat.
_____  Similar flora and fauna in all redstart habitats, unrelated to levels of 13C.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?

Gather Content
· What do you already know about habitat loss and songbirds?

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

__X__  Limited availability of habitat in areas where plants have low13C.
__X__  Higher insect biomass in areas where plants have low13C.
_____  A lack of territorial behavior being displayed by American redstarts.
__X__  Differences in food quality correlating with levels of 13C in the habitat.
_____  Similar flora and fauna in all redstart habitats, unrelated to levels of 13C.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses habitat loss and songbirds.
· What type of thinking is required?
        o This question is asking you to analyze the information given, using logic, to dissect the problem and determine the answer.
 
Gather Content
· What do you already know about habitat loss and songbirds?
        o Over the last 50 years, forest songbirds have declined severely, especially among long-distance migrants. These birds nest in northern forests in the summer, but spend their winters in South or Central America or the Caribbean Islands.
        o The culprit responsible for this widespread decline appears to be habitat fragmentation and loss, especially the availability of critical winter habitat in Central and South America.
        o Studies of the American redstart clearly indicate that birds with better winter habitat have a superior chance of successfully migrating back to their breeding grounds in the spring. In one study, scientists were able to determine the quality of the habitat that particular birds used during the winter by examining levels of the stable carbon isotope 13C in their blood. Plants growing in the best habitats in Jamaica and Honduras (mangroves and wetland forests) have low levels of 13C, and so do the redstarts that feed on the insects that live in them. Of these wet-forest birds, 65% maintained or gained weight over the winter.
        o By contrast, plants growing in substandard dry scrub have high levels of 13C, and so do the redstarts that feed in those habitats. Scrub-dwelling birds lost up to 11% of their body mass over the winter. Now here’s the key: Birds that winter in the substandard scrub leave later in the spring on the long flight to northern breeding grounds, arrive later at their summer homes, and have fewer young.
        o Thus, loss of mangrove habitat in the neotropics is having a quantifiable negative influence. As the best habitat disappears, over wintering birds fare poorly, and this leads to decreased reproduction and population declines.
        o Unfortunately, the Caribbean lost about 10% of its mangroves in the 1980s, and continues to lose about 1% per year. This loss of key habitat appears to be a driving force in the looming extinction of some songbirds.
 
Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o American redstarts primarily overwinter in Central and South America. The preferred wintering grounds are mangroves and wetland forests, which have lower levels of 13C. Plants in these habitats retain their leaves throughout the winter and is both a food source and a refuge for insects. There is strong competition among birds to secure territories in these habitats.
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o The question required you to analyze the information given, using logic, to dissect the problem and determine the answer.
        o Did you recognize that the different levels of 13C in the birds is a marker of food quality in their winter breeding grounds, and thus an indication of loss of high quality habitat?