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If I were the one who was interested in Spikes the 1st thing I'd do is look at the time of year I'd be hunting them & go from there! Late Oct. to Dec. I'd focus mostly on glassing & looking for groups of elk, snow for tracking these herds would be a plus. Cruising off road for elk sign (tracks) can be a plus. A single elk track would not be best at this time as rare is the case Spikes are alone at that time, look for several elk or larger groups & your odds will increase a spike is in the group. Late Fall & into Winter is not a profitable time to sit water in most areas for obvious reasons. Calling can work at that time but isn't your best bet, glassing & covering ground in variuos ways is.
If your spike hunt falls during the phases of the "rut" now calling can be a huge advantage once elk are located by sound or sight. (glassing) Too, getting into areas where fresh sign is around will enhance your odds. If sign is near feeding areas your best time would be first light to 1 1/2 hour after light. Then again the last 2 hours of daylight or evening. Look for meadows or parks big & small for such activity.
Active water sources or even wallows are a great time to sit during Aug. Sept. hunts as spikes, cows & other elk can frequent them. While sitting spots as these I would keep calling down to a minimum using light chirps & mews with no bugling.
If using "blind type setups" in these feeding areas or transition areas where elk travel to & from, yet elk aren't coming your way now you can introduce selective sounds to draw them over. At times social cow sounds will work but you can up your odds using sounds that require attention or aid from other elk instead of just social sounds.
One of these sounds is a separated calf chirp as you yourself mentioned. This sound does not require a special call, it can be done with a single reed mouth diaphragm or most external reed cow calls with a bit of practice. This sound can attract both cows & spikes first as opposed to mature bulls. Bulls can answer vocally letting this calf know where the herd is but rare is the case they show up 1st or at all. That's a big advantage to you the hunter! When calling is needed as this make sure your setup is in a good place where you're hidden from their view as to where sounds are coming from, you must have these approaching elk come look for you or these sounds! This distance will depend on your choice of weapon! Here's a clip of a separated calf sound, you can see how effective it can be when presented right!
http://www.elkheaven.com/video/calf-web.wmv
Another sound to consider at such areas as "blind type setups" to pull elk your way is the "estrus buzz" this is a sound elk will use especially cows when looking for another elk or group of elk, this sound can really attract attention to any elk within earshot & pull them your way. Once again especially cows & spikes 1st. Cows & spikes are very curious & will investigate other elk groups readily especially if they feel you are really an elk requiring assistance! That's key here, you're are playing on their desire to help out or aid you. Here's the sound!
As you can see from both clips elk will make & rely on selected sounds outside of social chirps & mews to find or attract other elk their way.
Setup is important in all cases & watch that you have the wind in your favor from where you expect their approach. I also like adding in natural elk sounds while calling such as light foot stomping & rustling limbs & brush as if there were elk milling around in the area.
Be willing to wait up to an hour after using such sounds during a setup, be patient & allow things to develop! Good Luck!
ElkNut1