Birds of North and South

     As I was held in the thrall of Costa Rica’s fascinating birds during our recent visit to that country, I got into reading what I could find about these amazing creatures with exotic crests, giant beaks, and extravagant appendages at the end of already-long tails.    

      I learned that many of these neotropical (the tropics of the western hemisphere) birds differ from their North American cousins in some interesting ways.

     The heart of the differences between birds of the north and those of Central America is that “neotropical birds do things slowly, much more slowly than their North American counterparts,” explains ornithologist Alexander Skutch.  For example, neotropical birds tend to have a much slower metabolic rate than do northern birds.  Probably related to the difference in metabolic rate, neotropical birds tend to live much longer than North American birds, on the order of two to three times longer.    

     In keeping with a slower life, the typical Central American bird’s first breeding is later than that of a typical North American bird.  And the ‘slower’ birds of Costa Rica incubate their eggs longer and care for their chicks longer than do most birds of North America.

      So what are the reasons for these differences between ’our’ birds of the north and those of Costa Rica? 

     The main reason for the differences appears to be climate.  The more ‘speeded up’ lives of North American birds helps them to survive in an environment where food is not abundant all year and where harsh winters force birds to work to stay warm.  A rapid metabolic rate generates needed body heat.

     The breeding differences also make sense in the different climates.  In the north, getting an early start on breeding increases the number of offspring a bird will likely produce in its lifetime.  And that’s important, since the lifespan of many North American birds is so short, only two or three years for many common species.  Likewise, a shorter incubation period and an earlier fledging for offspring, gets more birds ‘out there’ sooner.  A higher number of individuals strengthens the species as a whole against a harsher climate and frequent food scarcity. 

     Not only do neotropical birds start breeding later, incubate longer, and care for their young longer than do birds in northern climes, but they also tend to lay fewer eggs per clutch than their northern cousins, typically just one or two.  Scientists explain that predation of eggs is a bigger problem in southern climes than in North America.  An egg in a nest in Costa Rica is far more vulnerable to snakes and to a variety of mammals than are eggs in a nest in North America.  But by laying just a single egg, or two at the most, Central American birds lose fewer eggs to predation.  Many Central American birds ’make up’ for the small number of eggs per clutch by breeding several times a year, unlike northern birds, who are limited by climate in the number of clutches they can produce in a year.

     Another difference between Central and North American birds I found interesting is that far more Central American species engage in ‘lek’ breeding than do northern birds.  Lek breeding is when the males of a species gather in a particular area for the purpose of a competitive mating display.  Females visit the ‘arena’ and choose a mate from among the displaying males.  After mating, the male and female are done with each other.  The male plays no role in nest building, in helping the female during incubation, nor in caring for the young.  The reason lek breeding is much more prevalent in the neotropics than in North America, scientists say, is that food is so much more easily available in the warmer climate that the female does not need the male’s help the way northern female birds do, to help ensure their young’s survival.–April Moore

a chestnut mandibled toucan

a chestnut mandibled toucan

 

a mot-mot
a mot-mot

 

 

 

 

 

 

 

 

 

 

6 Responses to “Birds of North and South”

  1. George Elvin Says:

    April, I’m so happy to read about your Costa Rica adventure! Isn’t the wildlife amazing? And judging by this post, you know more about it than many of the guides we had on our trip. They were great, actually, and it was nice to be in a country where the majority of people really seem to be doing something to help preserve the environment. Keep up the good work, and I look forward to hearing more about your trip!

  2. Joan Kelly Says:

    This is great, April. Makes me wonder how it relates to humans living in both climates?

    Thanks.

  3. REX WILKINS Says:

    For those of you who find the Mot-Mot interesting :

    http://www.coraciiformestag.com/Motmot/momotus/momotus.html

  4. April Says:

    Thanks, Rex, for the link to more info on the mot-mot. I was surprised to learn that the little ‘appendages’ at the end of the tail aren’t ‘add-ons,’ but rather what remains after a section of each of the two long tail feathers falls out. Thanks!

  5. judy muller Says:

    Very interesting article, April. The mot-mot is really cool! I am happy for you that Tara and Lee decided to get married in Costa Rica, so you could have this beautiful experience.

  6. Elizabeth Cottrell Says:

    Fascinating, April! Thank you so much for digging beyond the surface to share this very interesting information. The next time we go to Panama to visit George Mobley, I’ve promised myself to get a guide to take me out bird watching.

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