Helping Managers Assess Vulnerability of Tidal Marsh Birds to Climate Change

In the project Vulnerability Analysis and Monitoring Program for Detecting Changes in San Francisco Bay Tidal Marsh Bird Populations researchers at PRBO Conservation Science developed the population-dynamic models needed in addition to habitat change projections to assess vulnerability of four tidal marsh-dependent species in the San Francisco Estuary: California Black Rail, California Clapper Rail, Saltmarsh Common Yellowthroat, and three tidal marsh-dependent subspecies of Song Sparrow; all species are California Threatened, Federally Endangered, or California Species of Special Concern. The researchers have made project results useful to managers to guide decision-making and prioritize potential management actions through a technical report summarizing findings and by creating a spreadsheet-based tool.

Above: Common Yellowthroat

The Simple Population Dynamic Model Tool makes it easy to explore a variety of potential outcomes for four tidal marsh-bird species. Get it here.
Results of the project:
The project included development of two types of models:
  • A Simple Population Dynamic Model Tool, for four tidal marsh species, with instructions for use, in spreadsheet format,
  • A more complex, population dynamic model for one of the four species, the Song Sparrow, which incorporates direct impacts of climate change, due to precipitation, temperature, and extreme tides.

A technical report describes how the models were created, how to use them, and relevant findings. A framework for monitoring impacts of climate change on tidal marsh birds will be completed in June 2013.

The interactive spreadsheet tool enables managers to (1) better understand the sensitivity of changes in population trend and viability in relation to changes in demographic parameters, including survival and reproductive success, and (2) evaluate the efficacy of proposed management actions to counteract threats to long-term viability for the four tidal marsh species studied.

Some Key Findings of the Population Dynamics Modeling Study:

For all four tidal marsh species the study found that:

  • Relatively short-term management actions (e.g., of a 20 year duration) can be effective in arresting and even reversing anticipated population declines.
  • Influencing population trends now can be an effective adaptation strategy for the future: A small reduction in predation on nests (by reducing predator populations or access of predators to tidal marsh nesting habitat) can be sufficient to counteract expected future population declines due to climate change. Moreover, improvement in nest survival represents a realistic management action that can modify current population trends, leading to, or enhancing population recovery.
  • Overwinter survival is also an important bottleneck and management actions may be able to benefit populations in this critical period of their annual cycle. The models demonstrate changes to viability and future trends as a result of modification to this demographic parameter.
    The more complex population dynamic model for Song Sparrows demonstrated that the most significant factor threatening the long-term viability of tidal marsh populations were extreme tides, but management actions to compensate for such mortality are feasible, and are also applicable to the other three marsh-bird species.
How Can I Use The Simple Population Dynamics Tool?
This spreadsheet tool was created to enable managers to better understand the sensitivity of population trends to changes in the underlying vital rates, and how population trend can be altered in relation to potential management actions or environmental change.

A set of instructions is included in the top worksheet of the file, explaining how to use the spreadsheet in one of three ways:

  • Change the value of one or more of the demographic parameters of the model to calculate the resulting population response,
  • Set a target population growth rate and determine the change needed in productivity or adult survival, or a combination of these parameters to achieve the target value,
  • Plot sensitivities - see how changes in adult survival or productivity will affect change in population trend, compared to current trend.

For help applying this tool and the results of the study to conservation planning, please contact Nadav Nur at

Contributors to this article
Last Updated: