Case Report: Independence day, comparison of methods to estimate the onset of dispersal in large territorial birds

Gallego-García, Diego; Watts, Bryan D.; Sarasola, José Hernán

doi:10.1186/s40317-025-00402-8

Animal Biotelemetry

Table 1 Description and comparison of the different methods used to estimate the onset of the post-fledgling dependence period in Chaco eagle fledglings tagged with GPS-satellite transmitters in central Argentina

From: Case Report: Independence day, comparison of methods to estimate the onset of dispersal in large territorial birds

ID	Type	ST	Description	PFDP	CV	Bias	Deviation	Effort	Reference
1	DT	0	First record over 10 km from nest	66.25 ± 25.09	0.38	− 179.00	179.00 ± 33.60	Low	(a)
2	DT	0	(1) and not within that distance for 5 records	99.00 ± 59.10	0.60	− 146.25	146.25 ± 59.49	Low	(a)
3	DT	0	(1) and not within that distance for 10 records	109.25 ± 79.32	0.73	− 136.00	136.00 ± 79.13	Low	Based on 1
4	DT	0	First record of the bird over 20 km from nest	215.00 ± 65.14	0.30	− 30.25	40.25 ± 67.64	Low	(b, c, d)
5	DT	0	(4) and not within that distance for 5 records	222.00 ± 51.27	0.23	− 23.25	33.25 ± 53.77	Low	Based on 4
6	DT	0	(4) and not within that distance for 10 records	222.00 ± 51.27	0.23	− 23.25	33.25 ± 53.77	Low	Based on 4
7	DT	1	Max (distance to nest/last record's distance to nest)	212.50 ± 35.71	0.17	− 32.75	32.75 ± 29.55	Low	This study
8	DT	1	Max (distance to nest/last 5 record's mean distance to nest)	224.75 ± 39.56	0.18	− 20.50	40.50 ± 8.74	Low	This study
9	DT	1	Max (distance to nest/last 10 record's mean distance to nest)	230.00 ± 42.39	0.18	− 15.25	35.25 ± 26.59	Low	This study
10	DT	0	First day with mean distance to nest of over 10 km	104.25 ± 81.52	0.78	− 141.00	141.00 ± 80.87	Low	This study
11	DT	0	(10) and not within that distance for 1 day	104.25 ± 81.52	0.78	− 141.00	141.00 ± 80.87	Low	This study
12	DT	0	(10) and not within that distance for 2 days	112.75 ± 94.26	0.84	− 132.50	134.50 ± 89.22	Low	This study
13	DT	0	(10) and not within that distance for 5 days	207.25 ± 70.51	0.34	− 38.00	40.50 ± 77.69	Low	This study
14	DT	1	Max (daily mean distance to nest /last day’s mean distance)	231.00 ± 10.23	0.04	− 14.25	14.75 ± 15.65	Low	This study
15	DT	1	Max (daily mean distance/last 2 days’ mean distance)	210.25 ± 68.06	0.32	− 35.00	61.50 ± 52.53	Low	This study
16	DT	1	Max (daily mean distance/last 3 days’ mean distance)	243.25 ± 44.87	0.18	− 2.00	30.50 ± 32.79	Low	This study
17	DT	1	Max (daily mean distance/last 5 days’ mean distance)	261.25 ± 20.35	0.08	16.00	16.00 ± 24.04	Low	This study
18	DR	0	Highest C.V. of distances to nest of 3 consecutive records	206.00 ± 49.28	0.24	− 39.25	39.75 ± 43.49	Medium	(c, d)
19	DR	0	(21) of 5 consecutive records	225.25 ± 39.92	0.18	− 20.00	40.50 ± 9.00	Medium	(c, d)
20	DR	0	(21) of 10 consecutive records	238.75 ± 29.62	0.12	− 6.50	27.00 ± 12.03	Medium	Based on 18
21	DR	0	Highest C.V. of the distances to nest of 1 day	222.00 ± 42.78	0.19	− 23.25	43.25 ± 29.76	Medium	Based on 18
22	DR	0	Highest C.V. of the distances to nest of 3 days	234.25 ± 6.95	0.12	− 11.00	11.00 ± 6.40	Medium	(e)
23	DR	0	Highest C.V. of the distances to nest of 5 days	243.00 ± 43.98	0.18	− 2.25	29.75 ± 32.99	Medium	(e)
24	DR	0	Day with the maximum distances traveled	267.25 ± 17.44	0.07	22.00	22.00 ± 10.80	Medium	This study
25	DR	1	Highest value of daily total distance /last day’s total distance	226.25 ± 53.99	0.24	− 19.00	26.50 ± 43.16	Medium	This study
26	DR	0	Week with the maximum distances traversed	262.50 ± 4.04	0.02	17.25	17.25 ± 9.88	Medium	This study
27	DR	1	Highest value of week’s /last week’s total distance	262.50 ± 9.04	0.03	17.25	17.25 ± 18.06	Medium	This study
28	RA	1	Visual comparison of weekly ranging areas	251.00 ± 11.60	0.05	5.75	5.75 ± 3.50	High	This study
29	RA	1	First record of week’s/last week’s ranging areas ≥ 20	248.50 ± 9.04	0.04	3.25	3.25 ± 2.99	High	This study
30	RA	1	Ranging area overlap of < 30% during three consecutive weeks	250.25 ± 15.52	0.06	5.00	7.50 ± 2.52	High	This study
31	RA	1	Ranging area overlap of < 20% during two consecutive weeks	259.50 ± 5.80	0.02	14.25	14.25 ± 8.96	High	This study

(a): Walls and Kenward [20]; (b): Ferrer [41]; (c): Soutullo et al. [23]; (d): Cadahía et al. [24]; (e) Engler and Krone [21]
Methods at the column “Type”; DT, distance-threshold; DR, displacement rate-based; RA, ranging areas. At the column “ST”, standardized (1) or not (0). PFDP, length of the post-fledgling dependence period, in days (mean ± standard deviation). CV, coefficient of variation. Bias, overall direction of the data: mean value of the deviations from the observed point of emigration (in days), with negative values underestimating and positive values overestimating the length of the PFDP): \(\Sigma Residual\)/n. Deviation = mean value of the absolute deviations from the observed point of emigration (in days): \(\sqrt{\Sigma {\left(Residual\right)}^{2}/n}\)). Effort = estimation of the relative amount of time needed to perform the computational analyses of each method. All methods describing maximum (highest) values, or first records, refer to the whole tracking study period (i.e. one calendar year since the moment the eaglet fledged from the nest)

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ISSN: 2050-3385

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