biology counter-current and cross-current systems in birds

Paper instructions:
You must use at least two journal article sources in each answer other than ones we used in class.  Of course you can use

any material from class but your answer must go beyond what we discussed in class.  Your answers must be typed and double-

spaced.  Obviously you must include full citations for the sources you use.  This should go without saying but do not

collaborate on your answers and do not plagiarize.

Distinguish between counter-current and cross-current systems in birds.  Give examples of each and choose one to describe

in detail.

What factors determine clutch size in birds.  Explain the differences in clutch size with latitude, i.e. birds near

equator have smaller clutches than those further north.