Migration routes
Within the study region, migration routes of 13 Common cuckoos (comprising 7 males and 6 females) were systematically documented from 2018 to 2021 (Table 1). Notably, two individuals, identified as 201907 and 202115, achieved successful completion of the autumnal migratory endeavor. Additionally, a singular representative, denoted as 201907, undertook a successful spring migration. Population of common cuckoo breeding in Central Asia manifest three principal autumn migration routes (Fig. 1), Specifically, 8 individuals (61.5% of the total) opted for the western route around the Qinghai-Tibet Plateau and the Taklamakan Desert. Notably, 201907 undertakes two consecutive autumn migrations, ultimately wintering in Tanzania. 2 Common cuckoos (15.4% of the total) choosed to traverse the Qilian Mountains from their breeding sites, proceeding southward over the Qinghai-Tibet Plateau via Xining. However, 1 individual lost its signal near Lhasa after reaching that vicinity. 3 common cuckoos (23.1%) selected for the eastern route, circumventing the eastern part of the Qinghai-Tibet Plateau. Notably, Common cuckoo 202115 successfully completed its autumn migration and accomplished wintering in Mozambique (Fig. 1). The difference in wintering locations between these two common cuckoos (i.e. identified as 201907, 202115) from the same breeding site implies, to some extent, a relatively weak migratory connectivity within the common cuckoo population.
Table 1
Common cuckoo Individuals Tracked from 2018 to 2021
Season | Birds ID | Tracker ID | Gender | Departure date | Arrival date | Migration distance (Km) | Tarsus(mm) | Wing(mm) | Weight(g) |
Autumn | 201801 | B008 | ♂ | 2018.8.3 | | 2268.31 | 22.25 | 180 | 98 |
201803 | B006 | ♀ | 2018.8.3 | | 2045.23 | 25.15 | 215 | 104.08 |
201804 | B007 | ♀ | 2018.8.15 | | 3279.48 | 23.48 | 200 | 92.86 |
201805 | B010 | ♂ | 2018.7.31 | | 1125.68 | 23.7 | 219 | 95.91 |
201906 | B011 | ♀ | 2019.7.29 | | 6248.16 | 23.54 | 205 | 90.67 |
201907(1st) | B012 | ♀ | 2019.7.31 | 2019.11.26 | 9459.45 | 24.28 | 201.2 | 95.26 |
201907(2nd) | B012 | ♀ | 2020.7.20 | 2020.11.19 | 9840.14 | | | |
202010 | B027 | ♀ | 2020.7.28 | | 1288.35 | 21.6 | 197 | 92.95 |
202111 | HQP3660 | ♂ | 2021.7.16 | | 4707.01 | 23.46 | 212 | 110.04 |
202113 | HQP3662 | ♂ | 2021.7.18 | | 2280.85 | 22.45 | 216 | 101.8 |
202114 | HQP3663 | ♀ | 2021.7.12 | | 2618.82 | 25.73 | 210 | 126.59 |
202115 | HQP3667 | ♂ | 2021.8.11 | 2021.12.7 | 11594.56 | 23.61 | 211 | 101.7 |
202116 | HQP3669 | ♂ | 2021.8.16 | | 6748.27 | 23.31 | 207 | 111.78 |
202117 | HQP3671 | ♂ | 2021.8.9 | | 2139.54 | 24.24 | 212 | 107.16 |
Spring | 201907 | B012 | ♀ | 2020.3.27 | 2020.5.13 | 9033.51 | | | |
202115 | HQP3667 | ♂ | 2022.4.2 | | 9197.32 | | | |
In the western route of autumn migration, the most utilized stopover site is situated in Hotan, Xinjiang (80.78E, 36.25N), with four Common cuckoos (identified as 201801, 201907, 202116, 202117) choosing this site for resting. On the eastern autumn migration route, the secondary hub for stopovers is Baoding City, Yunnan, China (99.23E, 25.46N), where three Common cuckoos (identified as 202010, 202103, 202115) were observed resting. In the central migration route, both Common cuckoos paused for rest in Delingha City, Qinghai, China (98.26E, 36.62N). Furthermore, Dinder National Park in Sudan (34.91E, 12.23N) represens the stopover site with the longest duration (46.5 days). Following the completion of spring migration, Common cuckoo 201907 did not return to its original breeding site in Guazhou County. Instead, it selected a new breeding site near Barkol Kazakh Autonomous County, Hami City, Xinjiang (91.19–94.48 E, 43.21–45.05N) (Fig. 2). During its second autumn migration, this individual chose stopover sites in Pakistan (Mangla, 73.59E, 33.17N), Eritrea (Gash-Barka, 37.56E, 15.27N), and Sudan (Dinder National Park, 34.91E, 12.23N), all of which are characterized by latitudinal proximity (Table 2).
Table 2
The main stopover sites and durations during the migration process of the Central Asian breeding population of Common cuckoos.
Season | Stopover site | Region | Longitude | Latitude | Birds | Arrive time | Departure time | Duration (day) |
Autumn | Hotan Prefecture | China | 80.78E | 36.25N | 201801 | 2018.8.24 | 2018.8.29 | 5.37 |
| | | | | 201907 | 2019.8.4 | 2019.8.10 | 5.75 |
| | | | | 202116 | 2021.8.1 | 2021.8.13 | 12.17 |
| | | | | 202117 | 2021.8.12 | 2021.8.20 | 8.25 |
| Kashi area | China | 76.49E | 38.66N | 201804 | 2018.9.1 | 2018.9.16 | 15.12 |
| Delingha | China | 98.26E | 36.62N | 201803 | 2018.8.7 | 2018.8.18 | 11.5 |
| | | | | 201805 | 2018.8.15 | 2018.8.25 | 10.25 |
| Baoshan | China | 99.23E | 25.46N | 202010 | 2020.8.12 | 20208.31 | 18.25 |
| | | | | 202113 | 2021.8.7 | 2021.8.27 | 20.75 |
| | | | | 202115 | 2021.8.18 | 2021.9.9 | 21.75 |
| Mangla | Pakistan | 73.59E | 33.17N | 201907(1st) | 2019.8.13 | 2019.8.27 | 14.5 |
| | | | | 201907(2nd) | 2020.7.27 | 2020.8.20 | 24.5 |
| | | | | 202116 | 2021.8.21 | 2021.9.3 | 13.42 |
| Pathankot | India | 75.81E | 35.54N | 201906 | 2019.8.14 | 2019.9.5 | 22 |
| Gash-Barka | Eritrea | 37.56E | 15.27 | 201907(1st) | 2019.9.14 | 2019.9.29 | 14.5 |
| | | | | 201907(2nd) | 2020.9.14 | 2019.9.26 | 12.5 |
| Dinder National Park | Sudan | 34.91E | 12.23N | 201907(1st) | 2019.9.29 | 2019.11.15 | 46.5 |
| | | | | 201907(2nd) | 2020.10.11 | 2020.11.6 | 26.5 |
Spring | Mambasa | Congo | 29.70 | 2.08 | 201907 | 2020.4.4 | 2020.4.18 | 13.25 |
| Agew Awi Zone | Ethiopia | 36.29E | 10.56N | 201907 | 2020.4.20 | 2020.4.28 | 7.5 |
| Sarayan | Iran | 58.19E | 33.18N | 201907 | 2020.5.1 | 2020.5.7 | 6.25 |
| Luuq | Somalia | 42.77E | 3,34N | 202115 | 2022.4.21 | 2021.4.25 | 4.25 |
Migrations traits
The results indicated that the Autumn migration distance of 201907 for the first and second subjects were 9459.45km and 9840.14km, respectively. However, the Autumn migration distance of 202115 was 11594.56km. We used independent sample t-test to compare Common cuckoo's autumn and spring migration (Fig. 3), a significant difference emerged in the migratory speed. Specifically, the spring migration speed was notably higher than that observed in autumn migration (spring speed: 789.80 ± 314.68 km/day, autumn speed: 548.61 ± 340.37 km/day, P = 0.002). Furthermore, the duration of stopover at intermediate sites during spring migration was significantly shorter compared to autumn migration (spring stopover duration: 9.97 ± 7.16 days, autumn stopover duration 13.28 ± 8.11 days, P = 0.01). However, there was no statistically significant difference in migratory straightness between spring and autumn migrations (spring straightness: 0.88 ± 0.13, autumn straightness: 0.88 ± 0.14, P = 0.21).
Statistical analysis of instantaneous speed data from 13 common cuckoos during migration in the period of 2018–2021, excluding data points with instantaneous speeds below 10 km/h, revealed distinct patterns. During autumn migration (Fig. 4), Common cuckoo migration predominantly occurred during the night, concentrated from 0:00 to 6:00 (84.77% of the total migration time). In contrast, during spring migration, the daily migration time span was concentrated from 0:00 to 12:00 (89.08%). There was no significant variation in the selection of migration routes based on the tarsus length and body mass of common cuckoos. However, wing length have a significant difference between various migration routes. Wing length of Common cuckoos that select middle and east migration routes is longer than individuals of west migration routes (Table 3).
Table 3
The impact of migration route selection on the response of morphological traits.
linear mixed model parameters |
Fixed effects | β ± SE | df | t | P |
Intercept | -0.893 ± 3.115 | 9 | -0.287 | 0.781 |
Tarsus length | -0.181 ± 0.149 | 9 | -1.216 | 0.255 |
Wing length | 0.033 ± 0.014 | 9 | 2.311 | 0.046 |
Body mass | -0.012 ± 0.016 | 9 | -0.765 | 0.464 |
Random effects | β ± SD | n | Results of VCA (%) |
sex | 0.001 ± 0.001 | 13 | 0.5 |
Residual | 0.199 ± 0.447 | 13 | 99.5 |
SE of fixed effects is the standard error of the mean; SD of random effects is the square root of the variance.