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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 124, No. 3. September 2012 
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FIG. 5. Body mass ol adult female Monk Parakeets exceeded that of males only during March-May, which 
corresponded to the period of egg-laying. 
competition and lack of divergent size or second¬ 
ary sexual characteristics (Collar 1997, Masello 
and Quillfeldt 2003). 
We noted incubation patches only among 
females, consistent with field observations that 
female parakeets, not males, incubate (Eberhard 
1998). Nestling Monk Parakeets in south Florida 
apparently undergo considerable recession of body 
mass prior to fledging (Fig. 4), consistent with 
findings from Argentina (Navarro and Bucher 
1990). This phenomenon has been documented in 
other Psittaciformes (e.g.. Burrowing Panot [Cya- 
noliseus patagonus], Masello and Quillfeldt 2002) 
as well as in seabirds and swallows (Ricklefs 1968. 
Ydenberg et al. 1995). and is believed to result 
from interactions between parental provisioning 
and nestling departure decisions (Morbev et al. 
1999). 
Successful invasive species possess behavioral 
attributes that enable them to adapt and exploit 
key resources in the non-native range (Wright 
et al. 2010). Monk Parakeet populations in the 
100 
pos^ibiemol^ro^isTootdf^ m3 ' e ^ Pdrakeets (dark bars > ^ h[| y lagged that of females (open bars). Maximum 
a ing complete replacement of primaries on both wings. Capped vertical bars denote I SE. 
