PALO DATA EXPLORER

Point Blue staff and interns collect weather data several times each day at the Palomarin Field Station to understand how climate change (over the long-term) and weather fluctuations (over the short-term) affect birds. Weather plays a huge role in the daily lives of birds, from successfully raising young to surviving the winter, while climate change can affect the long-term stability of bird populations.

Warming winters

Temperature data is collected multiple times each day at the Palomarin Field Station. To examine long-term weather patterns, calculated the annual average of the daily high and low temperatures since 1976, as well as the seasonal averages. Over the long term, the average annual temperature has been about 12.8ºC or 55ºF (see dashed line). Annual average temperatures and summer average temperatures have fluctuated, but there has been no long-term trend. In contrast, winter average temperatures have been rising steadily. We have also documented increasing high temperatures in winter months and decreasing high temperatures in summer months.

Average annual and seasonal temperatures recorded at the Palomarin Field Station (1976–2023)

Fluctuating rainfall totals

Rainfall totals are recorded each day at the Palomarin Field Station, and annual totals are calculated from July through June of the following calendar year, to capture an entire winter rainy season. Since 1976-77, annual rainfall totals have averaged 846 mm or about 2.75 feet (see dashed line) but have ranged widely. The wettest year we recorded was in the winter of 1997-98 (during a strong El Niño) with 1612 mm recorded (over 5.25 feet)! More recently, we had two very dry winters in a row in 2019-20 and 2020-21, the driest years since 1976-77, when only 352 mm were recorded (about 13.9 inches).

Annual precipitation totals recorded at the Palomarin Field Station (1976-77 through 2022-23)

Why is tracking weather and climate important for bird conservation?

Understanding how birds are affected by weather and climate requires long-term monitoring over decades. Because of our long-term bird monitoring and weather data collection at Palomarin, Point Blue has been able to identify changes in both the bird populations and the local climate, and uncover the links between them. This information helps us understand how well birds are adapting to climate change, and which species may be more vulnerable to climate change and may require more conservation attention. Here are just a couple examples of how our research has identified how birds are responding to global climate change.

Inconsistent Changes in Migration Timing

A changing climate may influence the seasonal timing (“phenology”) of blooming plants, hatching insects, and bird migration or nesting. In some cases, birds may not be able to easily change the timing of their migration to keep up with changes in the timing of their plant and insect food supplies, while others are shifting to try to stay in sync.

Spring arrivals. We have examined the dates migratory species arrive at Palomarin in the spring, and found that some species are arriving earlier (Orange-crowned Warbler), some are arriving later (Wilson’s Warbler), while others haven’t changed at all (Swainson’s Thrush).

The timing of bird arrivals in spring is thought to be adapted to the timing of food availability for successfully raising young, which may also be shifting with climate change. Earlier spring arrivals would be consistent with warming trends and an earlier onset of spring, although spring and summer temperatures have not changed much at Palomarin. However, birds also need to be in good enough body condition to migrate from their non-breeding grounds, and changes in habitat quality there or along their migration routes might create delays in their arrivals at Palomarin.

Fall arrivals. Among species that arrive at Palomarin in the fall, the timing of Fox Sparrow arrivals hasn’t changed at all, while Golden-crowned Sparrow and Ruby-crowned Kinglet are arriving significantly earlier. Hermit Thrush may also be shifting toward earlier arrivals. The timing of bird arrivals in fall likely reflect conditions to our north, with earlier fall arrivals suggesting an earlier end to their nesting season.

For all of these species, it’s not yet clear why some birds aren’t changing the timing of migration (yet), and whether birds that are shifting the timing of their migration are able to keep up with changes in their environment. Future research could examine whether individuals that arrive earlier or later are more successful in raising young or surviving the winter, whether the optimal arrival time has changed over the years, and whether it depends on how far the birds are migrating.

Changes in Body Size

Birds at Palomarin have been getting longer wings! We confirmed this surprising finding using banding data from both Palomarin and the San Francisco Bay Bird Observatory. Studies from other parts of the world have found that birds are getting smaller, thought to be related to increasing temperatures. Longer wings could indicate birds in California are getting larger, possibly in response to increasing variability in our climate or more favorable conditions than in other places.

To understand why birds have been getting longer wings, future research could examine whether birds with longer wings arrive at the Palomarin Field Station at different times than birds with shorter wings, or whether they are better at raising young or surviving the winter.

How did we collect these data?

The tools have changed over time, but we have been collecting weather data on site since 1968, including daily records of precipitation, fog, temperature, cloud cover, wind, and barometric pressure. The bird body size and arrival dates data come from our long-term mist netting and banding operation. All of these data are collected by staff, volunteers, and especially the hundreds of interns who have trained at Palomarin over the years.

Want to know more?

• Plan a visit! Our bird banding lab and nature center are open to the public, and you can join our scientists to learn how we collect this important data. Check here for more information about our current banding schedule and how to visit.
• Watch our webinar on this topic, part of our Science Stories from Palomarin webinar series.
• Read some of our related scientific publications:
  • Migratory bird arrivals. Pages 232–242 in Indicators of Climate Change in California. Nur N, Humple D, Salas L. 2018. Office of Environmental Health Hazard Assessment, California Environmental Protection Agency [View PDF]
  • Avian body size changes and climate change: warming or increasing variability? Goodman RE, Lebuhn G, Seavy NE, Gardali T, Bluso-Demers JD. 2011. Global Change Biology. [View at journal website]
  • Evidence of the effects of climate change on landbirds in western North America: A review and recommendations for future research. Seavy NE, Humple DL, Cormier RL, Porzig EL, Gardali T. 2018. Western Field Ornithologists. [View PDF]
  • Demographic responses to climate-driven variation in habitat quality across the annual cycle of a migratory bird species. Saracco JF, Cormier RL, Humple DL, Stock S, Taylor R, Siegel RB. 2022. Ecology and Evolution 12:e8934. [View at journal website]
  • Projecting demographic responses to climate change: adult and juvenile survival respond differently to direct and indirect effects of weather in a passerine population. Dybala KE, Eadie JM, Gardali T, Seavy NE, Herzog MP. 2013. Global Change Biology. [View at journal website] [Read summary]
  • Full list of Palomarin publications
• There is much more to learn from these data! Please contact us if you are interested in collaborating on future research.