Honors Theses

Date of Award


Document Type

Undergraduate Thesis



First Advisor

Lainy Day

Relational Format



Manakins are a family of birds the males of which use acrobatic, non-vocal display behaviors to attract females to mate. Across the manakin family (Pipridae), species perform displays of varying complexities with variation in the number and type of display sites, acrobatics, and number of mechanical sounds. Females of at least one species, select males on the basis of 10s of ms differences in performance of certain male display elements suggesting strong sexually selection. Additionally, recent studies show a positive relationship between display complexity and relative brain weight in manakins. This overall association of complexity with brain weight could be due to growth of many regions of the brain, concerted evolution, or individual brain regions may be driving this correlation, mosaic evolution. The arcopallium (AP), is a region likely to be specialized for display complexity. AP has both motor and limbic functions, and in oscines (songbirds), a specialized portion of the AP, the robust nucleus of the arcopallium (RA), is known to function in song production of vocal courtship displays. Manakins are suboscines that do not appear to have vocal learning or an RA. However, the AP has been shown to be larger in male golden-collared manakins which perform displays than in females that do not display. In addition, the AP in golden-collared manakins contains numerous androgen receptors similar to those found in the RA of songbirds, a trait not seen in other suboscines that do not have complex display. Thus, the AP in manakins is capable of responding to testosterone (T), and because display in manakins in known to be activated by T, the AP could play a role in the courtship behaviors of manakins. Another area, the Nucleus Taeniae (Tn) of the AP, could also be implicated in display complexity. Tn has been shown to have high concentrations of androgen receptors, and though considered part of AP, it is exclusively limbic and may have distinct function from AP. The volume of the nucleus rotundus (Rt), a visual thalamic nucleus, was used as the control since it was unlikely to be related to display complexity. We compared AP, Tn, and Rt volume of 12 different manakin species and the closely related ochre-bellied flycatcher; species were chosen for their varying display complexities. We found a significant positive relationship between AP volume and display complexity of the manakins' non-vocal courtship behaviors, but no relationship between Tn or Rt with display complexity.

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