788 
THE WILSON JOURNAL OF ORNITHOLOGY • Vol 124. No. 4. December 2012 
The Wilson Journal of Ornithology I24(4):788-792. 2012 
Hematocrit Does Not Indicate Condition in Nestling or Adult 
European Starlings 
Kayley D. Smith 1 and Colleen A. Barber 12 
ABSTRACT. Hematocrit, the percentage of packed 
red blond cells in blood, has been used as a measure of 
avian condition. We investigated the relationship 
between hematocrit and condition in a wild, breeding 
population of adult European Starlings (Sturnus vul 
Xcms). and their nestlings (at 5- and 11-days post hatch), 
Hemal writ was not correlated with condition in adults 
or nestlings at either 5- or 11-days post-hatch. Adult 
males and females had similar hematocrit values 
Hematocrit increased with age; adults had significantly 
higher hematocrit than both 5- and I I day old nestlings 
and 11-day old nestlings had significantly higher 
hematocrit than when they were 5 days of a«e 
Hematocrit was not correlated with sampling date 
ambient temperature, or relative humidity level, but was 
positively conelated with sampling time in the day for 
nestlings (but no. adults). Our findings caution against 
usmg hematocrit as a measure of condition in birds 
R ice,ved 30 November 20/1. Accepted 23 June 20/2. 
Hematocrit, the percentage of packed red blood 
cells m blood, characterizes the ability of blood to 
carry oxygen; increased hematocrit (within the 
normal range) results directly in increased oxygen 
carrying capacity (Birchard 1997), and has been 
positively correlated with energy expenditure 
(Viscor et al. 1985, Saino et al. 1997). Using 
ematocrit to assess avian condition would be 
advantageous as blood is easy to sample (Cuervo 
et al. 2011 ). and the procedure is inexpensive 
Several studies of birds have found a positive 
correlation between hematocrit and condition 
(when within normal range) (e.g.. Merila and 
Svensson 1995, Piersma et al. 2000). Others 
b ZT’ '! ave fOUnd n ° associat, °n (C.g., Dawson' 
and Bortolotti 1997. Amat et al. 2009), or have 
2007) e< H a Weak . ass ° cialion (e.g., Cuervo et al. 
(e^ M 0C ?‘ h3S bcen assoda,ed with die, 
(e.g., Men no and Potti 1998, Cuervo et al '>011) 
wVVoSnT (negalivdy: RichneTet al.’ 
793 positively e.g., Dawson and Bortolotti 
l " 7 ' reV ,ewed ** e, al. 2007). and 
’ Department of Biology. Saint Mary’s University 
R ob,e tree,. Halifax NS B3H 3C3, Canada ’ ‘ ^ 
Corresponding author; e-mail: colleen.barber@smu.ca 
dominance (e.g.. van Oort et al. 2007). all of 
which relate to condition. 
VVe investigated whether there was a relation¬ 
ship between hematocrit and condition in a wild 
population of nest box-breeding adult (male and 
female) and nestling (young vs. older) European 
Starlings (Sturnus vulgaris). This species is a 
facultatively polygynous passerine breeding in 
cavities; they typically have two broods a year 
(Kessell 1957). Both males and females incubate 
the eggs and provision the offspring (Feare 1984). 
Nestlings fledge when they are between 21 and 
23 days of age post-hatch (Cabe 1993). Our 
second objective was to examine if hematocrit 
dilleied between mule and female breeding adults 
and il it increased with age (nestlings vs. adults, 
and nestlings when 5 days of age vs. when 11 days 
ot age). The potential effects of sampling dale and 
linte o| day, ambient temperature, and relative 
humidity on hematocrit were also investigated. 
METHODS 
We studied a nest-box breeding population of 
European Starlings on the campus of Saint Mary's 
University in Halifax, Nova Scotia. Canada (44 
.1 54.07" N. 63 34' 47.09" W) from May to July 
■ ^ a ’ rs are double-brooded, but do not 
generally remain together for both broods: we 
, L felon, termed the first broods ‘early’ and 
second broods ‘later’. We checked nests daily 
unti egg-luyjng, then monitored nests every 3 days 
until 3 days prior to the estimated time of hatch: 
we then checked nests daily through day 15 of the 
neM ing period (checking nests after this time can 
result m premature fledging). 
We caught adults using a nest-box trap when 
nestlings were 5 days of age. All adults and 
nestlings were banded with a Canadian Wildlife 
Service band and three color bands for Individual 
identification. This study complied with CCAC 
guidelines and was approved by the Animal Care 
Committee at Saint Mary’s University (protocol # 
07). We took morphological measurements 
mass to the nearest 0.5 g with a Pesola spring 
