Where to bird in Otter Creek Marsh Area?

[Martha Jane]

We are always hearing there is such interesting birding along the Iowa River corridor in the Otter Creek Marsh area, but it's a pretty big area and we're not sure where to go. We would appreciate some suggestions for specific locales or walks in that area which might be of interest in general, and this time of year specifically. I found something with details like that on the internet a few years back, but am having no luck finding it now. Thanks in advance for any suggestions!