Diets of Three Sympatric Grebe Species in Lake Titicaca Indicate Possible Dietary Niche Partitioning

Dietary niche partitioning is a fundamental process in community ecology, of interest to both conservationists and ecologists. We present data on the dietary niches of three sympatric grebes from Lake Titicaca: the endangered endemic Titicaca Grebe <i>Rollandia microptera</i>, Rolland's Grebe <i>Rollandia rolland</i>, and the Silvery Grebe <i>Podiceps occipitalis</i>. This is the first study comparing the diets of these three species since 1981. We conducted stomach content analysis on 45 Titicaca Grebes, 30 Rolland's Grebes, and 15 Silvery Grebes, and quantified the degree of niche overlap among individuals and what prey classes were driving variation between species. Rolland's Grebe and the Silvery Grebe have a more invertebrate-based diet than the Titicaca Grebe. The use of presence-absence methodologies and numeric methodologies for counting prey items leads to different results regarding dietary differences between these species. While our dietary categories are too coarse to definitively prove it is a case of dietary niche partitioning, it is indicative of it. We suggest future avenues to prove dietary niche partitioning in these species, and how dietary studies could answer questions regarding this ecosystem's response to invasive species.