The effects of geolocators on return rates, condition, and breeding success in Common Sandpipers Actitis hypoleucos

Figures & data

Figure 1. Common Sandpipers carrying geolocators mounted parallel (left panel) and perpendicularly (right panel) to the leg. The bird in the left panel was tagged with a Lotek MK5040 geolocator in the UK; the bird in the right panel was tagged with a Migrate Technology Intigeo geolocator in Senegal.

Table 1. The effects of (a) carrying a geolocator compared with colour rings only and (b) carrying a geolocator mounted parallel or perpendicularly to the leg on: return rate, return date, change in body condition and hatching and fledging success in the year of attachment and year of recapture. The raw proportions and the standard errors (se) are in brackets. OR is the Odds Ratio statistic from the Fisher’s exact test.

a	No geolocator	Geolocator	Test statistic	P value
Return rate	54% (15/28)	59% (13/22)	χ^2= 0.011^b	0.918
Return timing	118.86 (±2.11se)	118.39 (±2.19se)	T = 0.153	0.880
Δ Body condition^a	0.64 (±1.20se)	−0.29 (±0.81se)	W = 30	0.827
Hatching success 2017	67% (4/6)	67% (8/12)	OR = 1	1.000
Fledging success 2017	25% (1/4)	36% (5/14)	OR = 0.616	1.000
Hatching success 2018	43% (3/7)	43% (3/7)	OR = 1	1.000
Fledging success 2018	14% (1/7)	43% (3/7)	OR = 1.810	1.000
b	Parallel	Perpendicular	Test statistic	P value
Return rate	70% (7/10)	50% (6/12)	χ^2= 0.265^c	0.607
Return timing	121.29 (±3.53se)	115.00 (±3.81se)	T = 1.247	0.239
Δ Body condition^a	−1.33 (±1.07se)	0.58 (±0.98se)	W = 10	0.429
Hatching success 2017	71% (5/7)	75% (3/5)	OR = 0.627	1.000
Fledging success 2017	0% (0/4)	43% (3/7)	OR = Inf	0.236
Hatching success 2018	33% (1/3)	50% (2/4)	OR = 1.810	1.000
Fledging success 2018	33% (1/3)	50% (2/4)	OR = 1.810	1.000

^aChange in body condition is calculated as the difference in an index of mass relative to tarsus length between 2018 and 2017, see methods.

^bConfidence interval for the difference of proportions = −0.37, 0.26.

^cConfidence interval for the difference of proportions = −0.29, 0.69.