Hens kept using two California-Nevada burns where survival fell

STEP 1 · Two fires

Location timing relative to each fire defines the periods

The Virginia Mountains study area covers 123,607 ha in Basin and Range country. That is about 305,400 acres. Vegetation runs from salt desert shrub at low elevation through pinyon-juniper to mountain shrub up high. The 2016 and 2017 fires burned 50,412 ha or 40.8 percent of the study area, about 125,000 acres. The Virginia Mountains Fire Complex started on 28 July 2016. The Long Valley Fire started on 11 July 2017 along Highway 395 about 25 miles (40 km) northwest of Reno. The caption marks before as 2008 through 2016. In the Methods, before and after follow when a location fell relative to a fire, so the printed years are a summary label. These results belong to this study population and these two fires.

Nest and hen comparisons used a before-after control-impact paired series. A point inside a perimeter was impact and a point outside it was control. Hens could cross that line and change class. The authors also note that birds in the burned and unburned groups were not independent of each other. Crews followed collared females about every three days from March through June and counted a nest successful if at least one egg hatched. Hens that hatched at least one egg were followed for up to 50 days after hatch. Our read treats the survival change as a first-years result on these two fires.

STEP 2 · Nest medians

Inside nest survival fell and the interval still includes a gain

The nest sample was 75 before the fires and 34 after. Before the fires 31 nests were outside the later burn and 44 were inside it. After the fires 18 were outside and 16 were inside. Our sum of the four groups is 109 nests. Cumulative nest survival outside the burns was 0.16 before the fires and 0.19 after. Inside it was 0.19 before the fires and 0.05 after. The inside interval after the fires runs from 0.00 to 0.28. Those figures are survival across a 37-day laying and incubation period. Over the same years unburned nest survival rose while burned nest survival fell and both moves feed the relative comparison.

The paired ratio was 0.21 with an interval of 0.01 to 2.50. The paper reports that median as a 79 percent drop in nest survival inside burned areas relative to unburned areas. The model put 90.2 percent of the posterior below 1. The authors tie the tail above 1 to a right-skewed distribution. An interval that includes a gain is not evidence the effect was zero. That 90.2 percent comes from all 109 nests and applies to these two fires only. Our read will not copy 0.05 onto the next fire as a forecast.

STEP 3 · Hen survival

Median paired before-after change was a relative decline of about 40 percent versus unburned ground

Yearling and adult female survival estimates used 178 radio-marked females. These estimates give cumulative annual survival modeled in monthly intervals. Hens could fall in more than one group over time so the authors do not give a clean bird count for each group.

Before the fires hens on ground that later burned survived at about 0.71 against about 0.79 outside, a gap of about 8 points. The 1999 Fish Springs fire largely overlapped these perimeters, though the authors only suggest that older fire effects may explain that weaker start. They did not test it.

After the fires the inside median was about 0.42 with an interval of 0.08 to 0.79. That annual estimate rests on 139 relocations. Outside the burns the results text gives 0.78 and the table gives 0.77 with the same interval of 0.54 to 0.99. The paired ratio was 0.60 with an interval of 0.12 to 1.40. The authors describe that median as about a 40 percent relative decrease inside the burns. The model put 88.9 percent of the posterior for the before-after ratio below 1.

The crew did not observe direct fire deaths of radio-marked adults from burning or smoke. They infer that most of the cost came from hens using the burn after the fire. Our read keeps this comparison on the 2016 and 2017 fires only.

STEP 4 · Still there

Hens nested in the burns while the survival medians were lower

The study found sage-grouse apt to reoccupy burned areas shortly after wildfire. Crews still found 16 nests inside the perimeters after the fires. A nest inside the burn shows use. Our read does not treat that nest as proof that survival held.

The authors did not directly measure population growth. They judge that nest and hen losses would likely compound into a decline for this population. The paper calls greater sage-grouse a species of conservation concern and places this population on the edge of the range. The authors say wildfire can raise the chance of losing that local population. Our use of the finding is observational. Hunting rules vary by state so check the state agency before any legal decision.

The paired analysis was built for nest and adult survival. The paper did not estimate brood survival. The authors suggest chicks could benefit from forbs on burns that resist annual grass invasion and that higher brood survival might offset other losses at first. Our read does not use that suggestion to cancel the nest median or the hen median. The authors also did not test the mechanisms behind the ratios.

STEP 5 · Summer glass

A paired look can change what you expect to see

Our suggested check sits after hatch in the stretch when this study still followed broods. Glass a burned drainage and a nearby unburned drainage with similar shrub on the same days. Record hens with chicks and hens without them from a distance. Never push birds and do not walk in on a nest.

A summer log can show whether hens or broods are using the burn. Our read is that steady use is a reason to keep glassing that drainage and to change a scouting expectation. It cannot show recovered nest or hen survival and it cannot test the 79 percent or 40 percent figures. Brood notes from the glass are not a brood survival estimate.

Our default for a large fresh burn in similar sage on this California and Nevada edge is not to treat hens using it as proof that hen or nest survival held. On these two fires the median estimates were lower relative to unburned ground, and the intervals were wide. We do not copy 0.05 or 0.42 onto that burn. Similar use on the burned and unburned drainages is a reason to expect birds in both places. It is not a reason to drop the survival caution. Glassing cannot replace the marked sample in this study. The rule is a starting expectation for a similar burn in the first years after fire.