Avian clutch size - the average number of eggs found in a particular (or comparable) bird species nest - often correlates with latitude.
The effect was discovered in the 1940s, and has been extensively researched since then. In general, comparable bird species near the equator lay approximately half as many eggs as those in northern temperate habitats.
There are at least seven theories - including the : • 'Food Limitation Hypothesis' • 'Nest Predation Hypothesis' • 'Skutch’s Hypothesis' • Ashmole’s Hypothesis, • 'Environmental seasonality' • 'Day length' • 'Egg-viability hypothesis'.
See: Wikipedia for details.
None of the theories yet has sufficient supporting field-evidence to be accepted as a definitive explanation.
Ideas for new topics, and suggested additions / corrections for old ones, are always welcome.
If you have skills or interests in a particular field, and have suggestions for Wikenigma, get in touch !
Or, if you'd like to become a regular contributor . . . request a login password. Registered users can edit the entire content of the site, and also create new pages.
( The 'Notes for contributors' section in the main menu has further information and guidelines etc.)