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Table 1.

Effect of corticosterone treatment and other parameters on primary, hand and tarsus growth rates and body mass and fat score increase of Eurasian kestrel nestlings

Primary growth rate
Hand growth rate
Tarsus growth rate
Body mass increase
Fat score increase
Explanatory variabled.f.Waldχ2-PWaldχ2-PWaldχ2-PWaldχ2-PWaldχ2-P
Age of oldest nestling in brood (days) 3 41.09 <0.001 90.78 <0.001 620.90 <0.001 156.59 <0.001 36.46 < 0.001 
Time of day (h) 1 2.36 0.124 2.37 0.123 3.46 0.063 14.43 <0.001 0.14 0.706 
Sex 1 3.86 0.049 3.02 0.082 2.85 0.091 17.27 <0.001 0.30 0.581 
Age difference to oldest nestling (days) 1 2.36 0.124 6.81 0.009 16.58 <0.001 18.86 <0.001 0.01 0.906 
Brood size 1 0.37 0.543 0.00 0.982 0.45 0.501 1.44 0.231 0.06 0.803 
Measure at day 10 (mm or g) 1 13.18 <0.001 15.06 <0.001 66.42 <0.001 11.61 <0.001 19.70 < 0.001 
Hatching date (day) 1 0.12 0.728 0.01 0.935 0.61 0.436 1.58 0.209 0.76 0.384 
Treatment group 1 102.82 <0.001 6.13 0.013 16.97 <0.001 49.44 <0.001 0.58 0.447 
Age × sex 3 3.92 0.271 5.99 0.112 11.04 0.012 3.09 0.377 0.64 0.888 
Age × age difference to oldest nestling 3 2.60 0.457 1.23 0.745 10.70 0.013 10.66 0.014 0.80 0.850 
Age × treatment group 3 85.00 <0.001 34.62 <0.001 105.46 <0.001 360.78 <0.001 8.99 0.029 
Sex × treatment group 1 0.97 0.324 0.46 0.498 0.26 0.609 0.01 0.923 0.01 0.917 
Age difference to oldest nestling × treatment group 1 1.14 0.287 1.28 0.258 0.01 0.928 0.30 0.581 0.06 0.800 
Age × sex × treatment group 3 0.75 0.860 5.71 0.126 2.50 0.476 6.38 0.094 0.78 0.854 
Age × age difference to oldest nestling × treatment group 3 3.27 0.352 7.57 0.056 2.37 0.499 2.14 0.544 7.05 0.070 
Primary growth rate
Hand growth rate
Tarsus growth rate
Body mass increase
Fat score increase
Explanatory variabled.f.Waldχ2-PWaldχ2-PWaldχ2-PWaldχ2-PWaldχ2-P
Age of oldest nestling in brood (days) 3 41.09 <0.001 90.78 <0.001 620.90 <0.001 156.59 <0.001 36.46 < 0.001 
Time of day (h) 1 2.36 0.124 2.37 0.123 3.46 0.063 14.43 <0.001 0.14 0.706 
Sex 1 3.86 0.049 3.02 0.082 2.85 0.091 17.27 <0.001 0.30 0.581 
Age difference to oldest nestling (days) 1 2.36 0.124 6.81 0.009 16.58 <0.001 18.86 <0.001 0.01 0.906 
Brood size 1 0.37 0.543 0.00 0.982 0.45 0.501 1.44 0.231 0.06 0.803 
Measure at day 10 (mm or g) 1 13.18 <0.001 15.06 <0.001 66.42 <0.001 11.61 <0.001 19.70 < 0.001 
Hatching date (day) 1 0.12 0.728 0.01 0.935 0.61 0.436 1.58 0.209 0.76 0.384 
Treatment group 1 102.82 <0.001 6.13 0.013 16.97 <0.001 49.44 <0.001 0.58 0.447 
Age × sex 3 3.92 0.271 5.99 0.112 11.04 0.012 3.09 0.377 0.64 0.888 
Age × age difference to oldest nestling 3 2.60 0.457 1.23 0.745 10.70 0.013 10.66 0.014 0.80 0.850 
Age × treatment group 3 85.00 <0.001 34.62 <0.001 105.46 <0.001 360.78 <0.001 8.99 0.029 
Sex × treatment group 1 0.97 0.324 0.46 0.498 0.26 0.609 0.01 0.923 0.01 0.917 
Age difference to oldest nestling × treatment group 1 1.14 0.287 1.28 0.258 0.01 0.928 0.30 0.581 0.06 0.800 
Age × sex × treatment group 3 0.75 0.860 5.71 0.126 2.50 0.476 6.38 0.094 0.78 0.854 
Age × age difference to oldest nestling × treatment group 3 3.27 0.352 7.57 0.056 2.37 0.499 2.14 0.544 7.05 0.070 

Data were collected from 109 nestlings in 30 broods. They were measured at the age of 10, 13, 16, 21 and 25 days resulting in 428 measurements. Growth rates per nestling were analysed using a repeated measures mixed model. Significant differences are in bold

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