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Research Article | Open Access

How does asymmetric sibling rivalry respond under environmental metal pollution? A case study of the Tree Sparrow (Passer montanus)

Jian Dinga,b, Shengnan Wangb, Wenzhi Yangb, Huijie Zhangb, Ni Wanga, Yingmei Zhangb()
School of Life Sciences, Henan Normal University, Xinxiang, 453007, China
Gansu Key Laboratory of Biomonitoring and Bioremediation for Environmental Pollution, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China

Peer review under the responsibility of Editorial Office of Avian Research.

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Abstract

The imbalanced allocation of maternal resources to eggs and nestlings may significantly impact the phenotype and fitness of offspring. Moreover, anthropogenic metal pollution has been reported to exert adverse effects on avian offspring. Therefore, we herein evaluated the relationships among offspring characteristics, asymmetric sibling rivalry, and the resulting offspring phenotype in a small passerine bird, Tree Sparrow (Passer montanus), at a polluted site (Baiyin, BY) and a relatively unpolluted site (Liujiaxia, LJX). By initiating incubation before the completion of clutch, asymmetric sibling rivalry might create a core and marginal offspring within the brood. In this study, lower egg mass, fewer core offspring, and more marginal offspring were found at the polluted site. Although eggshell speckling and coloration were relatively similar between the two sites, higher eggshell spotting coverage ratio and lower eggshell lightness (L*) and hue (h°) were observed in core eggs than in marginal eggs at the unpolluted site. The clutch size had a positive relationship with egg mass at the polluted site and with brood size at hatching at the unpolluted site. The differences in egg measurements across the laying orders in the samples were relatively large for larger clutch sizes. The core and marginal egg masses had a significant positive effect on the size of early core nestlings and late marginal nestlings at the unpolluted site. Fledgling rate was significantly positively related to the incubation period and nestling period, while negative relationship with mean spotting coverage ratio was found at the polluted site. Marginal nestlings at the polluted site showed a higher mortality rate. Overall, although asymmetric sibling competition strongly determines the variation of marginal offspring size, the effect is less dramatic in metal-polluted environments, providing some respite to wild birds that survive pollution-induced stress.

Keywords

Passer montanusEnvironmental metal pollutionOffspring characteristicsAsymmetric sibling competition

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Avian Research
Volume 16 Issue 1,
March 2025
DOI: 10.1016/j.avrs.2025.100225
Cite this article:
Ding J, Wang S, Yang W, et al. How does asymmetric sibling rivalry respond under environmental metal pollution? A case study of the Tree Sparrow (Passer montanus). Avian Research, 2025, 16(1). https://doi.org/10.1016/j.avrs.2025.100225
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Body size of the core and marginal nestlings at the two study sites (mean ± SD).

AgeNestling statusStudy siteBody mass (g)Body length (mm)Tail length (mm)Wing length (mm)Tarsus length (mm)Toe length (mm)Beak length (mm)
*: P < 0.05 compared to unpolluted site population; **: P < 0.01 compared to unpolluted site population.a: P < 0.05 compared to core nestling in the same population; aa: P < 0.01 compared to core nestling in the same population.
1-day-oldCorePolluted2.89 ± 0.7735.93 ± 2.25**0.92 ± 0.30**6.53 ± 0.576.41 ± 0.664.29 ± 0.423.43 ± 0.43*
Unpolluted3.04 ± 0.5437.96 ± 2.161.66 ± 0.496.56 ± 0.566.37 ± 0.434.50 ± 0.523.66 ± 0.39
MarginalPolluted2.61 ± 0.7335.42 ± 2.30*1.03 ± 0.426.39 ± 0.736.36 ± 0.624.32 ± 0.573.46 ± 0.39
Unpolluted2.68 ± 0.61aa36.84 ± 2.65a1.31 ± 0.516.32 ± 0.736.10 ± 0.65a4.31 ± 0.583.51 ± 0.39
5-day-oldCorePolluted10.41 ± 1.77**54.96 ± 4.25**2.92 ± 1.10**13.99 ± 2.32**12.35 ± 1.26**8.74 ± 1.17**5.64 ± 0.81
Unpolluted11.74 ± 1.8357.35 ± 4.193.50 ± 1.0515.49 ± 2.8012.99 ± 1.369.73 ± 1.255.60 ± 0.62
MarginalPolluted9.08 ± 2.71aa53.21 ± 4.47a2.74 ± 1.2013.17 ± 2.51*a11.95 ± 1.648.47 ± 1.35*5.79 ± 0.87**
Unpolluted9.34 ± 2.33aa53.90 ± 5.39aa2.96 ± 1.19a14.38 ± 3.05a12.11 ± 1.43aa9.28 ± 1.655.32 ± 0.44a
10-day-oldCorePolluted17.16 ± 2.14**81.86 ± 6.67**17.34 ± 3.89**36.89 ± 4.78**36.96 ± 3.91**11.58 ± 0.68**7.04 ± 0.62*
Unpolluted19.01 ± 2.3385.32 ± 5.6619.43 ± 3.9239.32 ± 4.4217.50 ± 0.6412.08 ± 1.037.23 ± 0.58
MarginalPolluted15.63 ± 3.17*aa77.75 ± 8.26*aa15.04 ± 4.32aa34.34 ± 5.97aa16.60 ± 1.17*a11.30 ± 0.82**a6.86 ± 0.68
Unpolluted17.05 ± 2.93aa81.07 ± 6.27aa16.57 ± 4.39aa36.24 ± 6.31aa17.12 ± 1.04a12.02 ± 1.137.08 ± 0.60
Growth rateCorePolluted0.55 ± 0.210.19 ± 0.12*0.48 ± 0.140.34 ± 0.100.44 ± 0.110.52 ± 0.170.30 ± 0.15
Unpolluted0.55 ± 0.140.16 ± 0.050.48 ± 0.110.34 ± 0.060.43 ± 0.130.51 ± 0.160.27 ± 0.12
MarginalPolluted0.54 ± 0.260.20 ± 0.08*0.44 ± 0.140.33 ± 0.060.42 ± 0.190.45 ± 0.160.29 ± 0.20
Unpolluted0.48 ± 0.10a0.16 ± 0.050.45 ± 0.100.32 ± 0.05a0.39 ± 0.110.50 ± 0.160.25 ± 0.07

Multiple regression analysis of the relationship between nestling size (PC1) of the 1-, 5-, and 10-day-old core nestlings and developmental and phenotypic variables.

Study siteIndependent variableDay 1Day 5Day 10
βSEPβSEPβSEP
β, the SE of β and the P value of a Student’s t-test of β are shown. Overall significance of the regression: polluted site: day 1, F = 1.389, P = 0.476, R2 = 0.650; day 5, F = 0.403, P = 0.862, R2 = 0.180; day 10, F = 0.502, P = 0.795, R2 = 0.215; unpolluted site: day 1, F = 3.381, P = 0.101, R2 = 0.802; day 5, F = 3.724, P = 0.033, R2 = 0.691; day 10, F = 1.052, P = 0.432, R2 = 0.296.
PollutedConstant−5.2655.3880.4323.6254.6120.448−0.2764.6390.954
Hatch date0.1600.5940.813−0.0740.5290.891−0.0560.5460.920
Clutch size−0.7911.0440.5280.6280.6470.3520.5840.6260.371
Mean mass of core eggs(g)2.4655.0320.673−1.9291.5780.247−0.2271.5510.886
Mean spotting coverage ratio of core eggs (%)−3.9363.4110.368−0.0402.2750.9861.9861.9890.339
Core brood size at hatching1.5131.5260.426−0.5630.7150.447−0.5020.6480.455
Marginal brood size at hatching1.0411.2600.496−0.3770.5430.502−0.7590.5160.170
UnpollutedConstant−8.5413.0440.038−14.7633.7490.003−1.7873.9210.655
Hatch date−0.3390.7640.6760.1840.5050.723−0.8410.5580.152
Clutch size0.1470.4520.7580.7770.3450.0480.4170.3840.295
Mean mass of core eggs (g)4.5041.2060.0145.0561.4220.0052.3031.4320.129
Mean spotting coverage ratio of core eggs (%)2.0932.0770.3601.1692.4100.6381.4532.6440.591
Core brood size at hatching−0.5310.3120.149−0.7730.3190.036−0.3980.3320.249
Marginal brood size at hatching−0.0540.2520.837−0.2880.2460.269−0.2270.2880.443

Multiple regression analysis of the relationship between nestling size (PC1) of the 1-, 5-, and 10-day-old marginal nestlings and developmental and phenotypic variables.

Study siteIndependent variableDay 1Day 5Day 10
βSEPβSEPβSEP
β, the SE of β and the P value of a Student’s t-test of β are shown. Overall significance of the regression: polluted site: day 1, F = 1.704, P = 0.415, R2 = 0.836; day 5, F = 0.487, P = 0.803, R2 = 0.245; day 10, F = 1.079, P = 0.447, R2 = 0.447; unpolluted site: day 1, F = 0.999, P = 0.501, R2 = 0.500; day 5, F = 0.562, P = 0.749, R2 = 0.457; day 10, F = 9.324, P = 0.005, R2 = 0.889.
PollutedConstant1.8524.2790.707−2.7735.0730.598−10.0235.2070.090
Hatch date−0.0040.5030.9950.1210.6140.8480.9030.6310.190
Clutch size0.4840.6420.5300.3090.8020.7090.1260.8020.879
Mean mass of marginal eggs (g)−4.0472.2430.2130.4212.1390.8482.9312.6640.303
Mean spotting coverage ratio of marginal eggs (%)−1.9544.2770.6930.5722.3070.8100.6003.1670.854
Core brood size at hatching1.4231.1620.345−0.3200.6990.658−0.7600.9100.428
Marginal brood size at hatching1.3410.7110.2000.0740.5360.893−0.4570.5460.427
UnpollutedConstant−5.3024.9950.329−9.2159.4490.385−4.1672.0120.077
Hatch date0.2120.9310.828−0.1821.9160.929−0.0400.2370.872
Clutch size−0.5790.5270.314−0.6010.8710.528−0.3190.1840.127
Mean mass of marginal eggs (g)2.4551.4430.1404.7393.2760.2222.4830.6190.005
Mean spotting coverage ratio of marginal eggs (%)−0.6052.6650.828−0.3064.9410.954−0.4771.0390.660
Core brood size at hatching0.1350.3320.6990.2860.8470.753−0.2210.1340.145
Marginal brood size at hatching0.8570.4710.1191.2151.2530.3870.8630.1830.002

Multiple regression analysis of the relationship among hatching rate, fledgling rate, and developmental and phenotypic variables.

Study siteDependent variableIndependent variableβSEP
PollutedHatching rateConstant0.8670.8750.341
Hatch date−0.0290.0610.637
Clutch size0.0940.0630.163
Incubation period (day)0.0450.0440.323
Egg mass (g)−0.4040.2760.169
Mean spotting coverage ratio (%)0.2300.2710.412
F = 0.721, P = 0.620, R2 = 0.231
Fledgling rateConstant4.2661.1150.004
Hatch date0.0840.0630.219
Clutch size−0.1010.0640.147
Incubation period (day)−0.1410.0450.012
Egg mass (g)−0.0410.2780.882
Mean spotting coverage ratio (%)0.6880.2830.038
Nestling period (day)−0.1520.0360.002
F = 6.580, P = 0.007, R2 = 0.814
UnpollutedHatching rateConstant1.0231.2500.424
Hatch date0.0840.0850.338
Clutch size0.0060.0590.926
Incubation period (day)−0.0680.0980.500
Egg mass (g)−0.0590.2760.832
Mean spotting coverage ratio (%)0.1310.5530.815
F = 0.318, P = 0.895, R2 = 0.086
Fledgling rateConstant3.3231.2100.017
Hatch date−0.0020.0820.979
Clutch size−0.0090.0630.143
Incubation period (day)−0.1180.0800.164
Egg mass (g)−0.0310.2420.899
Mean spotting coverage ratio (%)−0.1020.5690.861
Nestling period (day)−0.0770.0460.117
F = 1.076, P = 0.425, R2 = 0.332