The phenomenon of climate change is prompting songbirds to begin their nesting season earlier in the spring. However, this adaptation is coupled with an increased risk of encountering variable temperatures, including sudden cold spells and heatwaves. Research conducted by Cornell Lab of Ornithology indicates that such temperature fluctuations are causing a higher rate of nest failures, with young nestlings being particularly susceptible.
Increased Risks for Young Birds
Prompted by rising temperatures due to climate change, many songbirds have adjusted their nesting schedules to start earlier in the spring. This change, however, brings with it a heightened risk for nestlings: exposure to unpredictable temperature changes. These can take the form of both sudden cold fronts and intense heatwaves, leading to a higher incidence of nest failures. This conclusion stems from a recent study by Cornell Lab of Ornithology, reported on November 16 in Nature Communications.
Effects of Temperature Variability on Nest Success
Conor Taff, a co-lead author of the study and a researcher at Cornell University’s Department of Ecology and Evolutionary Biology, emphasizes that the impact of temperature changes goes beyond averages. “The interaction with immediate weather conditions, rather than long-term averages, poses challenges for all living beings, including humans,” he explains. Even a brief period of extreme cold or heat can be critical, regardless of average temperature trends. Differentiating between changing temperature averages and variability is vital in understanding climate change.
Study Methodology
The research team analyzed over 300,000 bird breeding records submitted to the Cornell Lab’s NestWatch project from 1995 to 2020. They identified the coldest and hottest three-day periods for each nest and examined how these extremes correlated with nesting success, defined by the survival rate of fledglings.
Key Findings
The study revealed that 16 out of 24 bird species experienced decreased reproductive success when either a cold snap or heat wave occurred during the incubation or nestling phases. Particularly affected were aerial insectivores, especially during cold extremes.
Challenges for Nestlings
Most birds feed insects to their young, which are vulnerable during cold snaps that reduce insect availability. In such conditions, adult birds might migrate to survivable areas, leaving eggs and nestlings exposed to cold and starvation. “Nestlings struggle during these periods as they cannot yet regulate their body temperature,” explains Ryan Shipley, co-author and a Ph.D. student at Cornell University at the time of the study. “Their rapid growth rate in the first weeks of life makes them particularly susceptible if insect activity declines due to a cold spell.”
Long-Term Implications
While examining a century’s worth of weather data, Taff and Shipley found no distinct pattern in the timing of temperature extremes but noted a general warming trend. Even if nestlings survive immediate temperature challenges, long-term health effects remain a concern. Past studies on Tree Swallows by the authors have linked temperature during development with growth rate and survival prospects, impacting their ability to migrate and reproduce in subsequent years. Therefore, shifts in temperature variability and breeding seasons can have significant implications for individual birds and entire populations.
Reference: “Inconsistent shifts in warming and temperature variability are linked to reduced avian fitness” by Conor C. Taff and J. Ryan Shipley, 16 November 2023, Nature Communications.
DOI: 10.1038/s41467-023-43071-y
Table of Contents
Frequently Asked Questions (FAQs) about climate change bird nesting
How does climate change affect songbird nesting patterns?
Climate change is causing songbirds to nest earlier in the spring, but this adaptation leads to increased exposure to temperature extremes such as cold snaps and heatwaves. These conditions result in a higher rate of nest failures, especially impacting young nestlings.
What are the main findings of the Cornell Lab of Ornithology study on songbirds?
The study found that 16 out of 24 bird species had reduced reproductive success when exposed to temperature extremes during nesting. Particularly, aerial insectivores were most sensitive to these changes, especially during cold weather.
Why are nestlings particularly vulnerable to temperature fluctuations?
Nestlings are vulnerable because they cannot regulate their own body temperature yet. Additionally, during the first weeks of life, they grow rapidly and require consistent insect availability. Cold snaps reduce insect activity, which can lead to starvation and higher mortality rates in nestlings.
Has there been a change in the timing of temperature extremes?
While the study examined a century of weather data, it found no clear pattern in the timing of temperature extremes. However, it noted an overall warming trend, which poses long-term consequences for bird populations.
What are the long-term implications of temperature variability on bird populations?
Temperature extremes during key developmental stages can affect a bird’s growth rate, body mass at fledging, and subsequent survival prospects. This influences their ability to successfully migrate and reproduce, impacting overall bird populations.
More about climate change bird nesting
- Cornell Lab of Ornithology Study
- Nature Communications Article
- Climate Change Impact on Bird Nesting
