DOI: 10.5061/dryad.vt4b8gtx4
title: Data for: Shy-boldness cannot predict egg rejection in the Japanese tit

description: In response to brood parasitism, which significantly reduces the
 reproductive success of avian hosts, hosts have evolved the ability to
 recognize and reject parasitic eggs. Many studies have revealed the
 influencing factors of egg recognition and egg rejection, and recent study
 found that host personality, along the bold-shy continuum, can influence
 egg rejection behavior. In addition, the egg rejection behavior of hosts
 differed among populations, suggesting that individuals with different
 personalities may evolve various adaptive behaviors under different
 parasitic pressures, but there has been few relevant experiments to verify
 this. In the present study, two populations of the Japanese tit Parus
 minor distributed in China were used to examine whether there were
 differences in egg rejection behavior of individuals with different
 personalities. The results showed that egg rejection rates of bold
 individuals (who remained in the nest box when encountering human
 invaders) and shy individuals (who immediately flew away from the nest box
 when encountering human invaders) were similar in both populations of the
 Japanese tit, and there were also no significant differences in egg
 rejection rates between individuals of the same personality in the two
 populations. This study suggests that host personality, along the bold-shy
 continuum, does not account for egg rejection behavior in the Japanese
 tits. This may be due to either other factors that affect egg rejection
 behavior counteracting the effect of personality, or the presence of
 multiple personalities that act together in the Japanese tits
 counteracting the effect of a single personality trait.
description: During the breeding season
 (April-June) of year 2022, when Japanese tits were found occupying nest
 boxes, breeding nests were regularly monitored to determine the dates of
 the first eggs. Female Japanese tits usually started incubation the day
 after laying their last egg (Zhang et al. 2020), and therefore, we defined
 the date when the females laid their last eggs as day 0 of the incubation
 period. After determining that the Japanese tits had entered the
 incubation period, we began an escape behavior test and a foreign egg
 recognition experiment among the female Japanese tits.
 In
 order to measure escape behavior, researchers slowly approached the nest
 box from about 10 m and gazed at the hole to record whether the females
 flew away, though the orientation of the approaching was adjusted
 according to location of focal nest boxes. If the female did not fly out
 from nest boxes when the experimenter went under the tree hung up nest
 box, we climbed the tree. We defined females that flew away from the nest
 box as shy individuals and those that did not as bold individuals during
 this process. If the females were not in the nest at the time of the first
 experiment, this experiment was repeated on the second day until escape
 behavior of the incubating females was recorded. 
          After waiting for the
 departure of the females, we placed one foreign egg in the nest cup after
 clutch completion (i.e., on the first day when the host began to incubate)
 (Figure 1a), while recording the experiment date and the clutch size in
 the experimental nest. In this study, most egg experiments were conducted
 on the day when the clutch of tits were completed or the next day, and
 only a small number of nests could not be determined for their incubation
 time. However, none of the experimental nests hatched after 6 days of the
 egg recognition experiment (see below), suggesting that all of these nests
 should have been in the early to mid-incubation period (i.e., 10-15 days
 for Japanese
 tits) at the time of egg
 experiments. The foreign eggs used in the experiment were the commercial
 non-fertilized eggs of white-rumped munia (<em>Lonchura striata</em>), colored with a blue non-toxic and odorless
 marker, which were slightly smaller in size than the experimental tit
 species (see Liu et al. 2019 for the exact egg sizes of Japanese tits and
 white-rumped munias). We set the length of the egg rejection experiment to
 6 days, and considered females of the experimental nest not to reject
 foreign eggs if the incoming eggs remained in the experimental nest and
 the nest was not abandoned within 6 days. Females of the experimental nest
 were considered to reject foreign eggs if within 6 days, the incoming eggs
 disappeared or remained in the nest box but the females did not incubate
 them (i.e., buried under the nest material or not in the nest cup, as
 shown in Figure 1b) (i.e., Yang et al. 2015; Liang et al. 2016; Liu et al.
 2019). Some studies have suggested that nest abandonment is also one of
 the ways host birds reject foreign eggs (Hanley et al. 2016), but nest
 abandonment was not found in our experiments. If the experimental nest
 succumbed to predation within 6 days, experimental results from that nest
 were not counted.
description: We used generalized linear
 models (GLMs) (logit-link function) to analyze the impact of escape
 behavior of the female
 Japanese tits on whether
 they rejected foreign eggs. The egg rejection behavior of the females
 (rejected=1; accepted=0) was the response variable. For analyses on the
 same population (i.e., in DZ or ZJ), escape behavior (escaped: shy; did
 not escape: bold), clutch size, and date of egg experiment were the
 explanatory variables. For analyses on the two populations combined,
 escape behavior, location, clutch size, and date of egg experiment were
 the explanatory variables. Likelihood ratio tests were used to obtain
 <em>p</em>-values. Data analysis was completed using R 4.1.0
 software, with a two-tailed test and a significance level of
 α=0.05.