The Wilson Journal of Ornithology 123 ( 2 ): 283 - 288 , 2011 
ALTITUDINAL VARIATION IN PARENTAL PROVISIONING OF 
NESTLING VARIED TITS (POECILE VARIUS) 
JONG KOO LEE, 1 OK-SIK CHUNG, 1 - AND WOO-SHIN LEE 1 
ABSTRACT.—We recorded parental provisioning rates of Varied Tits (Poecile various) at different altitudes (n = 17,7, 
and 11 nest boxes at 300. 900, and 1,400 m. respectively) to examine if males and females cooperate in response to 
increased provisioning pressure due to nutritional demands of nestlings. Females provisioned nestlings more than males 
irrespective of altitude. Provisioning rates of males and females tended to increase with elevation, but the increase was 
greater for males. Provisioning was low early in the nestling period, and gradually increased reaching a peak between 9 and 
10 days after hatching. The provisioning rate of females at the peak provisioning period (8—10 days) did not increase 
markedly at any altitude. Provisioning by males during the peak period increased and they contributed more during this 
period than at other times. The provisioning rate of males increased linearly with elevation. The provisioning rate of female 
Varied Tits also increased with elevation, but the increment ratio was lower thun that of males. Changes in provisioning 
rates with elevation may be due to the need to invest more in parental care under unfavorable environmental conditions, 
farents at high altitudes experience more difficulty provisioning, not only because of nestling growth, but also because 
provisioning is required more often. Thus, increased provisioning by males, which have a lower provisioning frequency 
relative to females, may be an investment to reduce foraging pressure on females and to ensure survival of nestlings. 
Received 30 June 2010. Accepted M December 2010. 
Newly-hatched birds depend completely on 
their parents for food. Thus, parental provisioning 
has a crucial role in survival of young (Bengtsson 
andRyden 1983, Keller and Van Noordwijk 1994, 
Wright et aL 1998). Parents rapidly adapt to 
changes in the environment by altering their 
provisioning rates and through cooperation with 
partners (Wright and Cuthill 1989, Davies 1991), 
Increases in provisioning rates can improve 
survival of nestlings, but parents may be at risk 
"t starvation and predation (Eggers et al. 2005). 
Stauss et al. (2005) reported higher costs were 
wcurred because of increased flying distance and 
provisioning frequency. Provisioning is a burden 
tor females and, during the nestling period, mass 
^ incurred by the female parent is linearly 
related to provisioning frequency (Nur 1984a, b). 
^his indicates it is necessary for females to 
achieve trade-offs between their energy costs 
^ Nnefits for nestlings (Badyaev and Ghalam- 
h°r 2001). Thus, it is important to examine if 
Provisioning frequency can be increased with 
minimal energy expenditure. Others have found 
Provisioning rate can change due to habitat 
quality, prey population density, prey size, and 
food availability (Nour et al. 1998; Grieco 2002; 
Tremblay et al. 2003, 2005). Provisioning rate is 
affected by gender of parents because sexual 
strategy and roles in nestling care differs (Kuitu- 
Departmeni of Forest Sciences, Seoul National Univer- 
5,[ y. Seoul 151-921, Republic of Korea. 
'Corresponding author; e-mail: nansamata@hanmail.net 
nen et al. 1996. Rytkonen et al. 1996. Grieco 
2001, Quillfeldt et al. 2005). 
Altitude contributes to environmental gradients 
and influences the ethology, morphology, and 
ecology of reproduction of a species. The ecology 
of reproduction of birds at high altitudes is 
considerably different from those at low altitudes, 
even of the same species (Cody 1966, Boyce 
1979, Badyaev 1997). Provisioning frequency of 
birds, in particular, increases at higher altitude 
because of environmental differences resulting 
from elevation (Badyaev and Ghalambor 2001). 
Parents at high altitudes experience more diffi¬ 
culty provisioning, not only due to nestling 
growth (Wittcnberger 1982), but also because 
feeding is required more often (Badyaev and 
Ghalambor 2001). Consequently, birds at high 
altitude have a greater challenge of reaching a 
trade-off between survival and reproduction than 
those breeding at low altitudes and strategies may 
reflect their gender. 
Varied Tits (Poecile yarns) are primarily 
resident and are distributed across Korea, Japan, 
and parts of China. Their habitats range from low 
to high mountains; they are socially monogamous 
and raise their young together (Yamaguchi and 
Kawano 2001). Thus, they are an appropriate 
species for study to examine the contribution of 
females and males in provisioning their young 
under the restriction of elevation. 
Our objectives were to examine: (1) provision¬ 
ing rates of Varied Tits at different altitudes, and 
(2) how males and females respond and cooperate 
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