The Wilson Journal of Ornithology 123(4):772-778, 2011 
INFLUENCE OF HATCH ORDER ON BEGGING AND PLUMAGE 
COLORATION OF NESTLING EASTERN BLUEBIRDS 
NATHAN SOLEY,' J LYNN SIEFFERMAN, 1,5 
KRISTEN J. NAVARA,' AND GEOFFREY E. HILL 4 
ABSTRACT.—Hatching asynchrony in altncial songbirds can influence the morphology and behavior of nestling birds. 
We compared the position of nestling Eastern Bluebirds f Sialici sialis ) in the hatching hierarchy to their (I) position in the 
egg-laymg order, (2) rate of nestling begging. (3) circulating corticosterone. (4) size, and (5) plumage coloration. Most 
nestlings hatched within 36 hrs of each other, and nestlings hatched in the order in which eggs were laid. Earh-hatched 
nestlings were heavier than late-hatched nestlings for the duration of the growth period and begged less intensely than their 
late-hatched siblings. There was little evidence of severe effects of hatch order. Hatch order did not influence nestling 
corticosterone levels nor did we find effects of hatch order on ornamental plumage coloration. Our data suggest nolone- 
term effect of hatching asynchrony on the development of sexually selected plumace coloration. Received 7 Jarman lull. 
Accepted 28 June 2011. 
Hatching asynchrony is common in many species 
of birds and results from incubation prior to clutch 
completion. Early-hatched nestlings are generally 
older and larger than their later-hatched siblings 
which creates a size hierarchy within the nest with 
early-hatched nestlings assuming a dominant role as 
later-hatched nestlings often grow slower (Clotfel- 
ter et al. 2000. Nilsson and Gardmark 2001, Saino 
et al. 2001. Magrath et al. 2003). Size hierarchies 
within broods often create differences in need for 
food among siblings, and offspring can use 
behavioral strategies to alter the rate al which they 
are provisioned. Nestling begging has been found to 
be an honest indicator of need (Price and Ydenburg 
1995, Lotem 1998, Saino et al. 2000). although this 
is not definitive across species (Wright et al. 2010). 
Successful begging behavior usually results in 
acquisition of more food and translates into an 
increase in mass (Kilner 1995). 
Hormones may be the proximate mechanism 
underlying variation in begging behavior. The 
nutritional state of nestlings is negatively corre¬ 
lated with activity of the hypothalamus-pituitary- 
adrenal axis in several species of seabirds (Nunez- 
de la Mora et al. 1996; Kitaysky et al. 1999 
1 Biology Depamnent, 572 Rivers Street. Appalachian 
State University, Boone. NC 28608. USA. 
2 Current address: Department of Plant Biology, 420 Life 
Science 11. Southern Illinois University. Carbondale !L 
62901. USA. 
•'203 Poultry Science Building, University of Georgia 
Athens. GA 30602. USA. 
a J , Depa I r ' me,u °f Biological Sciences. 331 Funchess Hall. 
Auburn University, Al 36849, USA. 
Corresponding author; 
e-mail: sieffermanlm@appstate.edu 
2001a). Experimental elevation of corticosterone 
has been shown to cause increased begging rates 
ol nestling Black-legged Kittiwakes {Rim tri- 
dactyla) (Kitaysky et al. 2001b). Late-hatched 
nestlings are assumed to experience nutritional 
stress and arc expected to increase corticosterone 
secretion, which in turn, should increase begging 
behavior (Maria and Holberton 1998. Kitayskvet 
al. 1999). 
Nestling condition also can be honestly sig 1 2 
naled by plumage coloration (Fitze et al. 2003. 
3 schirren et al. 2003, Jucot and Kempenaers 2007. 
Sicfferman and Hill 2007). Juvenal plumage 
coloration might function in parent-offspring 
communication and mediate parental favoritism 
either at the nest (Tschitren et al. 2003. Galvan et 
al. 2008. Griggio et al. 2009) or later during ihe 
post-fledgling dependence period (Tanner and 
Richner 2008, Ligon and Hill 2010). Nestling 
condition can have long-term effects by influenc¬ 
ing adult plumage used in sexual signaling, il 
nestlings retain portions of the juvenal plumage 
into adulthood. Parental strategies for maximizing 
fitness may include adjusting the relative invest¬ 
ment in juvenile males and females (Trivers and 
Willard 1973) by manipulating their positions in 
the laying order (Badyaev et al. 2002). 
Eastern Bluebirds (Sialia sialis) are sexuall) 
dichromatic songbirds that, on average, lay 4-5 
egg clutches in Alabama. Males display bright 
UV-blue structural coloration on the plumage ot 
their back, head, wings and tail while females 
display similar coloration but are duller overall 
Brighter individuals gain higher reproductive 
success as adults (Siefferman and Hill 2003. 
2005). Bluebirds in Alabama begin incubation on 
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