====== Avian clutch sizes and latitude ======

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 for why this might be - including :

  * The 'Food Limitation Hypothesis'
  * The 'Nest Predation Hypothesis'
  * 'Skutch’s Hypothesis'
  * 'Ashmole’s Hypothesis'
  * 'Environmental seasonality'
  * 'Day length'
  * The 'Egg-viability hypothesis'.

See: [[https://en.wikipedia.org/wiki/Avian_clutch_size|Wikipedia]] for details.

To date, none of the theories has sufficient supporting field-evidence to be accepted as a definitive explanation.

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Also see :[[content:life_sciences:zoology:tropical_colourfulness]]