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It looks like sustained or consistent moisture might be (at least part of) the phenological cue for flowering: The wikipedia article mentions that consistent humidity will induce flowering in at least some species and cites Fernández-Alonso & Groenendijk (2004), which says: It generally flowers after the rainy periods, but in humid pastures and under ...


7

There is no color code for the leafs - the color results from biochemical reactions. Basically there are three colors: Green, yellow and red. Green color is caused by the chlorophyll inside the chloroplasts, when the leafs are active in photosynthesis. Yellow color is caused by Carotenoids, which are present in the leafs all the time, but are masked by the ...


5

It's a nice question, I've tried looking for research papers to no avail. But I will add a few things that I hope will help: Firstly, tap water's composition is quite different from rain water- two criteria for distinction that come to mind would be pH and TDS, details follow: Tap water has a higher TDS (total dissolved solids)than rain water, making it ...


4

I don't know about the specific cues that American robins use for migration. This species is also both a short range (e.g. between states or to lower altitudes) and long range migrant (e.g. Florida & Mexico), so the cues that they use can probably differ between overwintering populations. There are also year-round populations of robins in the US, but ...


3

As the name implies, reflectance spectra are measured from light reflected off an object. Any object with reflects light, such as any opaque object) will work for this technique; to me this seems like solids are ideally suited for reflectance spectrphotometry. You might be used to transmission or absorbance spectrophotometry, which measures the amount of ...


3

There are various parameters that describe change of seasons such as day length, temperature, humidity. But it can be assumed that most of these parameters ultimately depend on one parameter- day length. The response of plants towards the length of day/night cycle is called photoperiodism (which dictates spring flowering). This article explains the effect ...


3

What There are two theories according to Jennifer Wells, Leaf Color Change: Competition theory - states that nutrients are redistributed to important parts of the plant. Lack of nutrients in the leaves will decrease the chlorophyll synthesis thus the leaves change their color. The redistribution does not happen equally that's why some leaves are ...


2

"Within-season variation" may be referring to one of two things (depending on the context): More commonly: the variation of a variable within a given season (i.e., between months or days within that season). Öst (1999) demonstrates an example of this use (in the context of breeding season). Less commonly: the variation of a variable between the same ...


2

I live in Boston, Massachusetts. At the Back Bay Fens, a couple of miles from downtown, the Muddy River is partly bordered with dense stands of Phragmites reeds. Back in the 1990s I discovered that robins nest among these reeds in spring. According to Cornell University's Laboratory of Ornithology, this is the only place in North America where robins are ...


2

I'm not a specialist in this area, but I would guess that the length of day-light periods compared to night time could be a good trigger. This is quite independent of the weather, is quite constant (even though length of days is known to have changed through over the millions of years past since the formation of earth).


1

What is the expected phenotypic trait of an offspring given the phenotypic trait of its parents? The expected trait of the offspring is equal to the mean of the parents traits. For this I assumed we don't have more information about the genetic of the trait (typically, without knowing the directionality of dominance and number). What is the expected ...


1

Thank you for these answers. My robin sightings decreased over the first few weeks since I wrote this, however they're back in full force now. This made me curious enough to do further research, and I happened upon two fact sheets about American Robins, whose scientific name is Turdis Migratorius, meaning Migrating Thrush. I've extrapolated data from a ...


1

idea 1) It's possible that some subset of your area has higher-scale / better resolution aerial photographs available. Could you find these and use them to test your model? idea 2) What geographical area / timescale are you looking at? For certain areas/times, you can get a bit of data on phenology from dated herbarium specimens (ie pressed plant ...


1

One can sometimes notice street lights delaying the annual shedding of leaves in some species (a well-lit branch will be mostly green while the rest of the tree is turning). So at least part of it would be day/night length in at least some species. I would expect, however, that the answer varies based on species, genus, and/or family, and that there are ...


1

Here is a good USDA link: http://www.usna.usda.gov/PhotoGallery/FallFoliage/ScienceFallColor.html It would appear that the shortening days are a main trigger, and there are other factors. I did a basic search using Google for "what triggers leaf fall in deciduous trees?", since I always thought temperature and changing seasons were major triggers and ...


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