UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934
(Amendment No. 3)*

Coresite Realty Corporation
(Name of Issuer)
 
Preferred Series A 7.25%
(Title of Class of Securities)
 
21870Q204
(CUSIP Number)
 
December 31, 2016
(Date of Event which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
☑
Rule 13d-1(b)
☐
Rule 13d-1(c)
☐
Rule 13d-1(d)

* The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).
 
CUSIP No. 21870Q204
13G
Page 2 of 5 Pages
 
1
NAMES OF REPORTING PERSONS
 
 
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
 
 
Heitman Real Estate Securities LLC, 36-4265577
 
 
 
 
2
CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
    
(a)☐
    
(b)☐
 
 
3
SEC USE ONLY
 
 
 
 
 
 
 
4
CITIZENSHIP OR PLACE OF ORGANIZATION
 
 
Delaware
 
 
 
 
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH
5
SOLE VOTING POWER
 
 
538,505
 
 
 
 
6
SHARED VOTING POWER
 
 
0
 
 
 
 
7
SOLE DISPOSITIVE POWER
 
 
538,505
 
 
 
 
8
SHARED DISPOSITIVE POWER
 
 
0
 
 
 
 
9
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
 
 
538,505
 
 
 
 
10
CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
 
 
☐
 
 
 
 
11
PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
 
 
11.7%
 
 
 
 
12
TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
 
 
Investment Adviser
 
 
 
 
 
CUSIP No. 21870Q204
13G
Page 3 of 5 Pages

Item 1.

 
(a)
Name of Issuer
   
Coresite Realty Corporation
     
 
(b)
Address of Issuer’s Principal Executive Offices
   
1001 17th Street, Suite 500, Denver, Colorado 80202

Item 2.

 
(a)
Name of Person Filing
   
Heitman Real Estate Securities LLC
     
 
(b)
Address of the Principal Office or, if none, residence
   
191 N. Wacker Drive, Suite 2500
   
Chicago, IL 60606
     
 
(c)
Citizenship
   
Delaware
     
 
(d)
Title of Class of Securities
   
Preferred Series A 7.25%
     
 
(e)
CUSIP Number
   
21870Q204

Item 3.
If this statement is filed pursuant to §§240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

 
(a)
☐
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).
       
 
(b)
☐
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).
       
 
(c)
☐
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).
       
 
(d)
☐
Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8).
       
 
(e)
☑
An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E);
       
 
(f)
☐
An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F);
       
 
(g)
☐
A parent holding company or control person in accordance with §240.13d-1(b)(1)(ii)(G);
       
 
(h)
☐
A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
       
 
(i)
☐
A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
       
 
(j)
☐
Group, in accordance with §240.13d-1(b)(1)(ii)(J).
 
CUSIP No. 21870Q204
13G
Page 4 of 5 Pages

Item 4.
Ownership.

Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.

 
(a)
Amount beneficially owned:  538,505
       
 
(b)
Percent of class:  11.7%
       
 
(c)
Number of shares as to which the person has:  538,505
       
   
(i)
Sole power to vote or to direct the vote  538,505
       
   
(ii)
Shared power to vote or to direct the vote  0
       
   
(iii)
Sole power to dispose or to direct the disposition of  538,505
       
   
(iv)
Shared power to dispose or to direct the disposition of  0

Instruction. For computations regarding securities which represent a right to acquire an underlying security see §240.13d-3(d)(1).

Item 5.
Ownership of Five Percent or Less of a Class.

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following     ☐.
 
Instruction. Dissolution of a group requires a response to this item.

Item 6.
Ownership of More than Five Percent on Behalf of Another Person.

Heitman Real Estate Securities LLC serves as an SEC-registered investment adviser or sub-adviser to various funds and separate account clients. Heitman Real Estate Securities LLC has been given dispositive power by its clients for the right to receive or the power to direct the receipt of dividends from, or proceeds from the sale of 538,505 shares, 11.7% of this issue.

Item 7.
Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company.
 
 
Item 8.
Identification and Classification of Members of the Group.
 
 
Item 9.
Notice of Dissolution of Group.
 
 
CUSIP No. 21870Q204
13G
Page 5 of 5 Pages

Item 10.
Certification.

 
(a)
The following certification shall be included if the statement is filed pursuant to §240.13d-1(b):
     
   
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.
     
 
(b)
The following certification shall be included if the statement is filed pursuant to §240.13d-1(c):
     
   
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

 
2/6/2017
 
Date
   
 
/s/ Randall Ramey
 
Signature
   
 
Randall Ramey
 
Chief Compliance Officer