From the Field:

2008 Research Under Way

Nesting Success Research 

June 2nd, 2008

As we reach the end of May, nesting activity is increasing across the study sites albeit slower than normal due to continued dry conditions. Blue-winged teal are now nesting along with northern shovelers while mallard and pintails are either renesting or near hatch for their initial nest. We have the first nests for mallards and pintails hatch across each of the crew areas. Study site 26 in the Woodworth crew area has done well with 4 mallard and 2 pintail nests hatched thus far. In the Goebel crew area, study site 46 has had 2 pintail, 1 mallard and 1 short-eared owl nests hatch to date. Not surprisingly, both of these sites have significant amounts of grassland on the site and in the surrounding area. However, to date our crews of located 398 total duck nests which is nearly half as many as were located by this time last year. Thunderstorms are beginning to roll across the prairies of North and South Dakota providing some much needed precipitation to help fuel growth of upland nesting cover but unfortunately we haven’t got enough to assist much in flooding temporary and seasonal wetlands that have been dry all spring. This week in From the Field, we will discuss the strategies birds employ during drought periods.

One of the big advantages that ducks have over many of the animals that call the prairie home is wings. This provides them with the ability to return to former breeding areas and assess conditions. If they are dry, like this year, they may continue on to explore other areas that may be experiencing the wet conditions necessary for a strong breeding attempt. If birds do choose to settle in an area where water is scarce, they may take advantage of more permanent water like that in semi-permanent wetlands. Because these wetlands are deeper, they warm slowly and bloom with invertebrate life later in the year. One strategy for the birds is to wait until invertebrates become more abundant and then breed later. There are distinct disadvantages to that strategy. Long-term research has shown that early nesting birds are those that contribute the most birds to the breeding populations. So in dry conditions, delayed breeding may be the only option but the odds are not stacked in the favor of later nesting hens. Additionally, if the hen hatches a nest, she may encounter poorer quality habitat for raising a brood during dry times. There is less flooded vegetation to provide cover and the food resources are less abundant for ducklings also. And if the nesting female loses her nest, she has more of a challenge in finding the food resources to lay another clutch during drier conditions. However, because most dabbling ducks are rather short lived, they take a big risk if they skip breeding for a year with dry conditions so most birds will make at least one breeding attempt. However, unsuccessful hens will not renest as frequently and may make an earlier migration to molting areas to molt their flight feathers to prepare for fall migration. A head start on these activities and skipping some of the perils of breeding may facilitate better survival throughout the remainder of the year and a chance to breed again under hopefully improved conditions.

We’ll see watch the signs as we move throughout the month of June for females to begin giving up on nesting for this year if wetland conditions don’t improve. The month of June is typically the peak of nesting activity for the whole suite of species that breeds here in the Dakotas. So check back in to see if conditions improve and how the birds respond.