Migration distance, migratory and breeding phenology in Icelandic waders
Data files
Mar 06, 2026 version files 188.68 KB
-
breeding_phenology.csv
179.50 KB
-
mean_temperature_arrival_period.csv
321 B
-
mean_temperature_breeding_period.csv
1.58 KB
-
migratory_phenology.csv
2.85 KB
-
README.md
4.42 KB
Abstract
Recent changes in phenology are widely reported across taxa, particularly in relation to migration and breeding, and rates of change are often greatest in species migrating over shorter distances. Species migrating over longer distances might be less able to advance breeding phenology, if they arrive on the breeding grounds later and breed very soon after arrival, but opportunities to quantify trends in timings of arrival and breeding across species that vary in migration distances but experience similar environmental conditions in their breeding area are rare. Several internationally important populations of waders, spanning a wide range of migration distances, breed in Iceland. Decades of monitoring of the phenology of these populations provide a unique opportunity to explore the links between migration distance and phenology. Timings of first spring arrival and egg laying were collected for common waders breeding across lowland Iceland from 2007 to 2022. Information on migration distances were collated from the literature or from individual tracking of different populations. Waders wintering closer to Iceland arrive significantly and substantially earlier in spring than those wintering further away. However, the difference in lay dates among these species is, on average, only ~1-2 weeks, because the timing of breeding of early-arriving species varies with spring temperatures substantially more than later-arriving species. Timing of laying is advancing more in short- than long-distance species while, over this survey period, time of arrival advanced more in long-distance than short-distance species. Consequently, short-distance migrants are breeding earlier despite little advance in arrival, while long-distance species are arriving earlier but showing little advance in lay dates. The longer arrival-laying gap in species travelling shorter distances therefore appears to provide opportunities to breed early in warmer springs that are not available to species travelling further and arriving later. Among migratory species, population declines are currently more evident in long-distance than short-distance species. Given the benefits of breeding early in migratory systems, including opportunities to re-nest following failure and greater recruitment rates of early-fledged offspring, the opportunity of arriving sufficiently early to take advantage of warming springs could be contributing to these divergent population trajectories. Quantifying the phenology of nest success and fledging of species migrating over different distances will help to identify the costs of travelling further and arriving later during this period of rapid environmental change at high latitudes.
Dataset DOI: 10.5061/dryad.qz612jmtn
Description of the data and file structure
The datasets used in this study contain phenological information for nine common wader species that breed across the Icelandic lowlands and migrate over different distances; Eurasian Oystercatcher (Haematopus ostralegus), Snipe (Gallinago gallinago), Golden Plover (Pluvialis apricaria), Redshank (Tringa totanus), Black-tailed Godwit (Limosa limosa), Ringed Plover (Charadrius hiaticula), Dunlin (Calidris alpina), Whimbrel (Numenius phaeopus) and Red-necked Phalarope (Phalaropus lobatus).
Migration distance
For each species, migration distance was considered as the distance between approximate mid-point of Iceland and the wintering area that holds the highest concentration of the Icelandic population. Measured in kilometers.
Migratory phenology
In southern Iceland, first arrival dates (FAD) have been recorded at Laugarás (64° 7′ N, 20° 30′ W) for most of the species, and Laugardalur (64° 13' N, 20° 43' W) for Ringed Plover, Dunlin and Phalarope, since 1988 and 2018, respectively. Each day, a standardised observation route was walked and driven four times a day throughout the arrival period of these species at both sites and first individuals of each species seen or heard were recorded.
Breeding phenology
From April each year (2007 – 2022), nests were located through surveys across lowland Iceland throughout the breeding season of all the species in each year. Laying date (i.e., the date when the first egg was laid) was estimated by back-calculating from incubation stage, using standard egg-floating techniques and assuming species-specific incubation period and egg laying interval; or observed hatching dates (for monitored nests that survived until hatching; n = 14%). GPS positions were recorded for most nests (n = 5859), but for 134 nests only the region where they were found was documented (S, SW, W, NW, NE).
Spring temperature data
We extracted the monthly mean of the daily mean temperatures (in Celcius (°C)) from March to June for the period 2007 and 2022 for five weather stations operated by the Icelandic Meteorological Office (www.vedur.is): Eyrarbakki (S), Keflavik (SW), Reykjavik (W), Bolungarvik (NW) and Raufarhöfn (NE); the closest stations to the breeding study locations. We then used the mean of the March and April temperatures to estimate the temperature during arrival (arrival temperature, at), and the mean of April, May and June to estimate the temperature during laying (laying temperature, lt), periods that reflect the arrival and nesting periods in Iceland
Files and variables
File: migratory_phenology.csv
Description: Each row represents the arrival date into Iceland for each species
Variables
- species: species name
- Year: year of the observation
- distance: migration distance of each species (km)
- FAD (first arrival date): observation of the first individual of each species seen or heard (ordinal date)
File: breeding_phenology.csv
Description: Each row represents the estimated laying date for each nest found since 2007
Variables
- species: species name
- Distance: migration distance (km)
- Region: region where the nest was found (S, SW, W, NW, NE)
- Year: year of each nest found
- ord 1 egg estimate: estimated laying ordinal date (i.e., the date when the first egg was laid)
File: mean temperature arrival period.csv
Description: Each row represents the annual mean temperature (°C) during the arrival period (March- April)
Variables
- Year: year
- mean_temp: mean of the March and April means of the daily mean temperature (°C)
- se_temp: standard error
File: mean temperature breeding period.csv
Description: Each row represents the annual mean temperature (°C) during the laying period (April, May and June)
Variables
- Year: year
- mean_temp: mean of the April, May and June means of the daily mean temperature (°C)
- se_temp: standard error
Code/software
Data were analysed in R 4.0.2 (R Core Team, 2020). Packages lme4 (Bates et al., 2015) and *lmerTest *(Kuznetsova et al., 2017) were used for the mixed models, and the package performance (Lüdecke et al., 2021) was used to check model’s assumptions.