Migratory birds advance spring arrival and egg-laying in the Arctic, mostly by travelling faster

In the current, warming climate many organisms in seasonal environments advance their timing of reproduction to benefit from resource peaks earlier in spring. For migrants, the potential to advance reproduction may be constrained by their migration strategies, notably their ability to advance arrival on the breeding grounds. Recent studies show various changes in migration strategies, including wintering closer to the breeding grounds, earlier departure from the wintering grounds or faster travels by spending less time on stopover sites. However, whether such changes lead to earlier arrival or earlier breeding remain open questions. We studied changes in migration and reproduction timing in 12 populations of nine migratory birds, including seabirds, shorebirds, birds of prey and waterfowl breeding on Arctic sites bordering the Greenland and Barents Sea, a region undergoing rapid climate warming. Timing of migration and reproduction was derived from tracking and field data, and analysed ..., We gathered data on the timing of spring migration and egg-laying to local snowmelt timing for a suite of arctic-breeding bird species, using a large set of tracking data supplemented by field data on egg-laying dates. Rather than using tracking data of individuals tracked from the non-breeding grounds and breeding across the entire breeding range of a species, the focus was placed on tracking data of individuals breeding at specific Arctic breeding sites. In this way, we aimed to reduce variation in the timing of arrival in the Arctic caused by variation in breeding location (e.g., Conklin et al., 2010).
Study species and sites
Our dataset contained tracking data (519 spring migrations of 274 individual birds) from 12 populations and nine migratory bird species, breeding at seven Arctic study sites in the Barents and Greenland Sea region from the period 2007 - 2023. For this paper, we treat each species at a separate study site as a separate population. The species and study sites incl..., , # Migratory birds advance spring arrival and egg-laying in the Arctic, mostly by travelling faster

[https://doi.org/10.5061/dryad.w0vt4b93d](https://doi.org/10.5061/dryad.w0vt4b93d)

## Description of the data and file structure

Data on migration and reproduction phenology were extracted from bird tracking data and compared with the date of 50% snowmelt at breeding sites. From this, we analysed how migration and reproduction phenology changed over time and with the rate of 50% snowmelt. From tracking data also travel speed and distance between non-breeding and breeding sites were also calculated to analyse whether changes in arrival date in the Arctic could be explained by earlier departure dates, faster travel or shorter distances between wintering and breeding sites.

### Files and variables

**1.snowmelt.csv**

1. date of 50% snowmelt in spring as extracted from 500m resolution MODIS Terra Surface Reflectance Daily Global product (MOD09GA)

1) NDSI_threshold Normalized difference ...,

在当前气候变暖的背景下，诸多栖息于季节波动环境中的生物会提前繁殖时序，以利用春季更早出现的资源峰值。对于迁徙鸟类而言，其提前繁殖的潜力可能受迁徙策略制约，尤其是能否提前抵达繁殖地的能力。近期研究揭示了迁徙策略的多种变化，包括在离繁殖地更近的区域越冬、提前离开越冬地，或是通过减少中途停歇地停留时间来加快迁徙速度。然而，这类变化是否能促成更早抵达或提前繁殖，仍是尚未解决的问题。

本研究针对栖息于格陵兰岛与巴伦支海周边北极繁殖地的9种迁徙鸟类的12个种群展开，涵盖海鸟、滨鸟、猛禽与水禽，该区域正经历快速气候变暖。本研究的迁徙与繁殖时序数据源自追踪记录与野外观测数据，并加以分析……我们针对一系列北极繁殖鸟类，收集了春季迁徙时序与产卵日期数据，并结合当地融雪时间；数据以大量追踪记录为基础，辅以产卵日期的野外观测数据。

相较于采用从非繁殖地追踪、且覆盖某物种全部分布繁殖区的个体追踪数据，本研究聚焦于在特定北极繁殖地繁育的个体追踪记录。通过该设计，我们旨在降低因繁殖位点差异引发的北极抵达时序变异（如Conklin等，2010）。

## 研究物种与样地
本数据集包含2007年至2023年间，在巴伦支海与格陵兰海区域7处北极研究样地繁殖的9种迁徙鸟类12个种群的追踪数据（274只个体的519次春季迁徙记录）。本文将每个研究样地的单一物种视为一个独立种群。研究物种与样地包括……，# 北极迁徙鸟类主要通过加快迁徙速度提前春季抵达与产卵时间
[https://doi.org/10.5061/dryad.w0vt4b93d](https://doi.org/10.5061/dryad.w0vt4b93d)

## 数据与文件结构说明
迁徙与繁殖物候数据源自鸟类追踪记录，并与繁殖地的50%融雪日期进行比对。基于此，我们分析了迁徙与繁殖物候随时间变化的规律，以及其与50%融雪速率的关联。此外，我们还通过追踪数据计算了非繁殖地与繁殖地之间的迁徙速度与距离，以探究北极抵达日期的变化是否可通过更早的出发时间、更快的迁徙速度或更短的越冬-繁殖地距离来解释。

### 文件与变量
**1.snowmelt.csv**
1. 春季50%融雪日期，数据提取自分辨率为500米的MODIS Terra地表反射率每日全球产品（MOD09GA）
1) NDSI阈值（Normalized Difference Snow Index，NDSI） 归一化差分雪盖指数……