Birds of a feather flock together, but what about their mites?

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Birds are one of the most well-studied organisms in the world. To date, it is estimated that nearly 10,000 species of birds exist worldwide! In Las Cruces, a biological station found in southern Costa Rica, records indicate that there are over 400 species of birds from 71 different families that reside in the nearby 266 hectare forest.

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Costa Rican’s national bird: Clay-Colored Robin; generalist feeder

Each bird species may have its own suite of ectoparasites including lice, mites, fleas, and ticks. Scientific literature shows that the biology of bird ectoparasites is still not well understood despite their important cost and role in a bird’s life (Proctor and Owens 2000). A bird’s feathers serve as a great habitat for ectoparasites, especially mites, and quantifying parasite type and number can be completed in several ways, many of which are non-invasive.

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Checking wings for mite eggs.

According to Whiteman and Parker (2012), there is a positive relationship between host density and parasite infestation but I have found little literature examining the relationship between host feeding type and parasite infestation .The objective of my study was to investigate and see if there is a relationship between bird parasitism and bird feeding behavior. I hypothesized that bird parasitism would correlate with feeding behavior, e.g. nectarivore.

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Rufous-Tailed Hummingbird; nectarivore

I captured a total of 81 birds representing 42 different species at two sites near Las Cruces Biological Station in Southern Costa Rica. Both sites were located approximately 4 km from the Panama border, site 1 was in an old coffee plantation and site 2 was in a privately owned 2 hectare section of primary forest.

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Site 1- Old coffee field now used to grow bananas, peppers, yucca, and berries.

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Site 1- Recently cleared paddock adjacent to old coffee plants.

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Site 2- Primary forest.

Birds were safely captured using 20 mist nets each 12 m long. Birds were identified to species and classified as generalist, nectarivores, insectivores, frugivore or grainivore feeders. For each bird, I examined the first four primary flight feathers on one wing for mite eggs. The presence of mites was quantified on a scale of 0 to 5, where 0 signifies that no mite eggs were present and 5 signifies that eight or more mite eggs on average were found on each feather.

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Blue Crowned Motmot; generalist feeder

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Scaly-breasted Hummingbird; nectarivore

Common Pauraque

Common Pauraque; insectivore

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Bay Headed Tanager; frugivore

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Yellow Faced Grassquit; Grainivore

Using Tukey’s HSD test, I found a significant relationship (P˂ 0.001) between bird feeding behavior and the number of mites present! Specific significant differences in parasite loads were observed between nectarivores and frugivores (P˂ 0.001), nectarivores and generalist feeders (P ˂ 0.001), and nectarivores and insectivores (P˂ 0.001). Significant differences were not observed between other types of feeding behaviors.  These results are consistent with my hypothesis that bird feeding behavior correlates with bird parasitism.

So, why is it important to study and understand ectoparasite and bird host relationships? Parasitism over time can impose a long-term cost to their hosts (Brown et al. 1995). With little understood about the biology of some of these parasites it may be uncertain the actual cost faced by the bird host. It is vital that future research further investigate the relationship and effect of ectoparasites on their bird host(s).

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