July Flowering Phenology

by Carl Strang

July was the last month in which I collected phenology data from Mayslake Forest Preserve. The results provided a satisfactory conclusion.

Many of Mayslake’s prairie plants first open their flowers in July.

Many of Mayslake’s prairie plants first open their flowers in July.

First flower dates become less different among years as the summer progresses, and that was true this year as well. The median difference from 2014 was 0 days for 47 species, an insignificant 2 days earlier than in 2013 for 31 species and the same vs. 2011 for 37 species, 1 day later than in 2010 for 37 species, and a slightly larger 5 days earlier for 35 species in comparison to 2009. The odd early year of 2012 continued to be the outlier, but even that difference was down to 10.5 days for 38 species.

Michigan lily provides one of the preserve’s more extravagant floral displays.

Michigan lily provides one of the preserve’s more extravagant floral displays.

All those medians were smaller than those for June, except the one for 2013, which was the same.

 

June Flowering Phenology

by Carl Strang

First flower dates at Mayslake Forest Preserve in June continued the trend of convergence on earlier years that is typical of the progressing season. The median difference from 2014 for 71 species was only one day earlier, and two days earlier than 2013 for 69 plant species.

Butterfly weed was among the species that first opened flowers in June.

Butterfly weed was among the species that first opened flowers in June.

The biggest difference continues to be with the very early year of 2012, but that is down to a median of 11 days later for 71 species. The difference for the remaining three years is not large: 5 days earlier than 2011 for 61 species, 5 days later than 2010 for 49 species, and 6 days earlier than 2009 for 51 species.

Compass plants began to bloom just before the end of June.

Compass plants began to bloom just before the end of June.

These differences represented reductions of 6 days, 3 days, 7 days, 1 day, and 4 days from May values for the years 2014-2010. The difference for 2009 increased by 3 days.

May 2015 Phenology

by Carl Strang

April’s phenological signal held true in May’s first flowering dates. This year continues to run ahead of most, but not by much.

Ohio buckeye was among the plants that bloomed in May.

Ohio buckeye was among the plants that bloomed in May.

Median first flower dates this May at Mayslake Forest Preserve were 7 days earlier than last year (54 species), 5 days earlier than in 2013 (70 species), 18 days later than in 2012 (69 species), 4 days earlier than in 2011 (68 species), 7 days later than in 2010 (45 species), and 3 days earlier than in 2009 (46 species).

Common spiderwort is peaking now, but started blooming in May.

Common spiderwort is peaking now, but started blooming in May.

The respective numbers for April were, in the same order: 6 days earlier, 9 days earlier, 25 days later, 6 days earlier, 9 days later, and 3 days earlier. On the whole this shows the usual trend of convergence among years as the season progresses.

A number of sedges first bloomed in May, including the small yellow fox sedge.

A number of sedges first bloomed in May, including the small yellow fox sedge.

Phenology First Take

by Carl Strang

One of the best ways of assessing how a given year compares with previous ones is by looking at first flowering dates. With April now complete, I can review those for Mayslake Forest Preserve. On the whole, this April can be regarded as slightly early, thanks to significant early warm days melting the snow and warming the soil.

Dutchman’s breeches bloomed abundantly at Mayslake this year.

Dutchman’s breeches bloomed abundantly at Mayslake this year.

Comparing median first flower dates in April places 2015 6 days earlier than 2014 (11 species), 9 days earlier than 2013 (20 species), 6 days earlier than 2011 (21 species), and 3 days earlier than 2009 (17 species). This April was 9 days later than 2010, and a substantial 25 days later than the anomalous warm year of 2012.

Most of these differences are not very large, and the expectation is that they will gradually diminish over the coming months.

Spring Progresses

by Carl Strang

After the spring beauties broke winter’s long suppression of wildflowers, other plants quickly have begun to bloom at Mayslake Forest Preserve.

Bloodroot is a popular subject for nature photographers. Seed-carrying ants have been spreading this species in several directions from one initial colony in the south savanna.

Bloodroot is a popular subject for nature photographers. Seed-carrying ants have been spreading this species in several directions from one initial colony in the south savanna.

Bloodroot is one of many plants in several families which convergently have evolved little edible handles called elaiosomes on their seeds. The ants carry the seeds to their nests, and after consuming the elaiosomes discard (plant) the seeds.

Dutchman’s breeches likewise are spreading impressively from their starting point.

Dutchman’s breeches likewise are spreading impressively from their starting point.

The year’s earliest sedge to bloom on the preserve, the common oak sedge, also is flowering, here surrounded by white trout lilies and cutleaf toothworts.

The year’s earliest sedge to bloom on the preserve, the common oak sedge, also is flowering, here surrounded by white trout lilies and cutleaf toothworts.

The trout lilies and toothworts are flowering now, along with common blue violets and others. So far these few species are pointing to an average to slightly early year as measured by flower phenology at Mayslake.

Spring at Last

by Carl Strang

My own idiosyncratic reckoning gives us 6 seasons in the Chicago area: spring, summer, fall, early winter, mid-winter and late winter. Subjectively, at least, winter seems to take up half the year, and that was truer this year than most. Late winter begins March 1, but its length varies greatly from year to year. My equally subjective designation of the first day of spring is when I see the first native wildflower blooming away from buildings. This year, as it happens, that date was my birthday, April 17, and was marked by two of the 3 usual species.

I saw spring beauties first. For once, the delicate pink of the flower is not overexposed in this image.

I saw spring beauties first. For once, the delicate pink of the flower is not overexposed in this image.

Some common blue violets were intermixed with the spring beauties.

Some common blue violets were intermixed with the spring beauties.

Though many individuals had open flowers that day, cold weather had held them back from opening sooner. The third species, which sometimes blooms first, is the white trout lily. Though abundant leaves were up by the 17th, I did not see flowers until Monday of this week.

June Flowering Phenology

by Carl Strang

Already by this point in the season it is clear that first flowering dates are converging, the differences among years becoming smaller by the month. Nevertheless, this year’s median June difference from last year (among 69 species) was 14 days, a full 2 weeks later (the May difference was 24 days).

Staghorn sumac first opened flowers on June 14 at Mayslake Forest Preserve this year.

Staghorn sumac first opened flowers on June 14 at Mayslake Forest Preserve this year.

Musk thistle, less desirable in the landscape but beautiful nevertheless, first bloomed on the same day.

Musk thistle, less desirable in the landscape but beautiful nevertheless, first bloomed on the same day.

Last year was an anomaly, a hot dry spring following a mild winter. When this year’s first flower dates are compared to those for the previous 3 years, the differences are much less. Flowers appeared a median 1.5 days earlier than in 2011 (62 species), 5 days later than in 2010 (45 species), and 4 days earlier than in 2009 (50 species).

May Phenology 3: Bird Arrival Dates

by Carl Strang

The pattern in the past has been for migrant bird arrival dates to be more similar between years than is true of flower and insect first appearances. Birds are capable of making small adjustments, but in general they are following the dictates of photoperiod, which observes the same calendar each year. Median arrival dates were thus only 3 days later at Mayslake Forest Preserve in 2013 than in 2012 (16 species), 8.5 days later than in 2011 (20 species), 1 day later than in 2010 (19 species), and 9 days later than in 2009 (19 species).

The eastern wood-pewee matched the median difference in arrival dates for both 2010 and 2009.

The eastern wood-pewee matched the median difference in arrival dates for both 2010 and 2009.

The respective differences for April and earlier were 7, 3, 2.5, and 5 days. The pattern of past years was sustained in magnitude, but it is also true that all median arrival dates were later in 2013 than in the other years. The late development of flowers and emergence of insects probably accounts for this. The birds can adjust their migratory timing that much.

May Phenology 1: First Flowering Dates

by Carl Strang

The end of May brings the next opportunity to compare seasonal timings between 2013 and the previous years. There’s nothing special in this choice, except that months are a familiar common language and they provide a sensible number of comparisons each year. The data I collect are limited to Mayslake Forest Preserve, because I am out in that property most regularly and so can make the most consistent comparisons. Today I’ll share the first flower dates, which provide the soundest results.

As expected, flowering phenology this May was much later than last year, a median 24 days later for 73 species. This is 10 days less than the April difference, but it is typical for the first flower dates to converge as the season progresses.

The broad-leaved woolly sedge, Carex pellita, was the median species this time.

The broad-leaved woolly sedge, Carex pellita, was the median species this time.

If we jump to the other early year, 2010, the difference also is less. The median first flower date was 12 day later in 2013 than in 2010 (54 species). The corresponding difference in April was 17 days.

Yellow sweet clover fell on the 12-day median difference.

Yellow sweet clover fell on the 12-day median difference.

The surprise came from the comparison between 2013 and the other late years, 2011 and 2009. The median difference was exactly 0 days for 2011 (67 species), and 2013 was only one day later than 2009 (53 species; the respective differences were 4.5 and 5 days in April).

Common spiderwort first bloomed one day later in 2013 than it did in 2009.

Common spiderwort first bloomed one day later in 2013 than it did in 2009.

All of this continues to underline how unusual last year was.

Bird Arrival Phenology

by Carl Strang

On Friday I shared this year’s flowering phenology through the end of April. There have not been enough first appearances of insects yet to make a comparison to previous years, but birds have been arriving at Mayslake Forest Preserve for more than a month. Most of these are species that winter in the southern U.S., and so are capable of tracking the weather conditions and adjusting their migratory jumps accordingly. Consequently the dramatic differences we see among years in plants’ first flowering dates are not reflected in the arrival dates of birds.

The first pine warbler appeared 7 days later in 2013 than in 2012.

The first pine warbler appeared 7 days later in 2013 than in 2012.

That said, the median difference between this year and last for the 31 species I could compare was 7 days later in 2013. One week, compared to nearly 5 weeks for first flowers, seems small, though it should be added that the range of arrival date differences was large, from 70 days earlier to 37 days later.

The first killdeer appeared 3 days earlier in 2013 than in 2010.

The first killdeer appeared 3 days earlier in 2013 than in 2010.

That 7 days’ difference was the largest in recent years. Median arrival dates in 2013 were 3 days later than in 2011, 2.5 days earlier than in 2010, and 5 days later than in 2009 (34 species in each case). All the ranges were large, in fact all were larger than for 2013 vs. 2012. Nevertheless, it would be hard to build a case that bird arrival dates varied much from year to year.

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